| MESOZOIC MAMMALS; Woutersiidae and Docodonta, an internet
directory: |
PLEASE NOTE: THIS PROJECT IS NOT SCIENTIFIC. IT IS A HOBBY.
"I was looking for information on an old mammal and found this lot. What is this
project?"
It's got lots of information on old mammals. For a short bit of background information, see
here.
| The genera on this page represent small, basal and generally early
mammals; or more strictly speaking, members of Mammaliaformes Rowe, 1988, rather than of Mammalia
itself, (McKenna & Bell, 1997). As with other basal
furry colleagues, the typical 'reptilian' jaw joint,
(articular-quadrate), was still residually
present, alongside of the characteristic mammalian one,
(dentary-squamosal). |
A. Woutersiidae B. Docodonta
| Taxon: Woutersiidae Sigogneau-Russell & Hahn, 1995
Reference: Sigogneau-Russell & Hahn (1995), Reappreciation of the Late Triassic
symmetrodont mammal Woutersia. Acta Palaeontologica Polonica 40(3), p.245-260.
Remarks: The only known genus of this family of mini insectivores. It was placed inside
the Superlegion of Kuehneotheria McKenna, 1975.
However: "Subsequently, Butler (1997) referred Woutersia to Docodonta. In my
opinion, molars of Woutersia could be structurally
antecedent to Docodonta, but Woutersia itself should not be formally included in
that group (see Martin and Averianov in press). Woutersia molar morphology is
structurally intermediate between those in morganucodontids and docodonts, and this taxon
is better maintain(ed) in the monotypic Woutersiidae", (Averianov, p.710).
Martin and Averianov has now been published. They don't place this genus within Docodonta.
However, they do conclude that docodonts may well have been descended from an ancestor that
was at least Woutersia-like. Some discussion on this is included in the entry below
for Tashkumyrodon.
Sigogneau-Russell, 2003 (p.373), seems to say that a linkage between Woutersia and
Docodonta 'appears unsatisfactory.' |
| Genus: Woutersia
Sigogneau-Russell D, 1983
'for Wouters'
Remarks: The genus has been seen as a possible and strange
'symmetrodont'. The molar cusps have as obtuse-angled triangular arrangement, and the
teeth have large cingula with further cusps; one on uppers
and two on lowers, (Kemp 2005, p.166). |
| Species: | Woutersia mirabilis Sigogneau-Russell D, 1983 |
| Place: | Saint-Nicolas-de-Point
/ Varangéville & Habay-la-Vielle & Syren |
| Country: | France & Belgium & Luxembourg |
| Age: | Norian (late) - Rhaetian (early), Upper Triassic |
| Remarks: | Small isolated teeth, (length ca. 1,5mm). The
holotype is a left lower molar, which resides at the Muséum
national d’Histoire naturelle de Paris (MHNH). |
| Reference: | Sigogneau-Russell (1983), A new therian mammal from the
Rhaetic locality of Saint-Nicolas-de-Port (France). Zool. J. of the Linnean Soc 78,
p.175-186. |
| Species: | Woutersia butleri Sigogneau-Russell D & Hahn
R, 1995 |
| Place: | Saint-Nicolas-de-Point |
| Country: | France |
| Age: | Norian (late) - Rhaetian (early), Upper Triassic |
| Remarks: | These teeth are even smaller than those of W.
mirabilis, the first named species. The holotype is also at the MHNH, Paris. |
| Reference: | Sigogneau-Russell & Hahn (1995), Reappreciation of the
Late Triassic symmetrodont mammal Woutersia. Acta Palaeontologica Polonica 40(3),
p.245-260. |
A. Woutersiidae B. Docodonta
Taxon: Docodonta Kretzoi M, 1946 sensu McKenna & Bell,
1997
Reference: Kretzoi (1946), On Docodonta, a new order of Jurassic Mammalia. Annales
Historico-Naturales Musei Nationalis Hungarici, Vol 39, No.1, p.108-111.
Or somebody else
Remarks: A probably better alternative would be to credit the authorship of the order to
Patterson in the 1950s. "First nomenclatural proposal of an order Docodonta was
actually by Kretzoi, but on inadequate grounds and without personal Study of any of the
forms involved", (Simpson GG, 1959, p.407).
Affinities
The placement of docodonts in the mammalian/near-mammalian
scheme of things is a bit unclear. There seems general agreement that they're further
derived than Sinoconodon, and most -though not
all- studies have concluded that they're more 'mammalian' than the
morganucodontids too, (see Pascual et al 2000,
p.407-408 for a brief summary of opinions). Be that as it may, they were fairly basal
beasties. The persistence demonstrated by Reigitherium, (late Upper Cretaceous of
Patagonia), is striking. However, there is much disagreement that it really is a docodont.
Briefly summarized, these animals had primitive jaws with relatively sophisticated
dentition.
The meaning of docodont
The name of the group refers to the 'beam'-teeth; upper
molars which are "strongly broadened transversely," Martin & Nowotny
2000, (p.93). The authors carry on to report: "This broadening of the teeth led to an
increase in the chewing area in the teeth of docodonts, which enabled the animals to
effectively crush their food. However, the docodonts could not crush their food in the
same way as rodents or large herbivores (ungulates), since their jaws did only allow very
restricted transversal or longitudinal movement." This means that while they'd
developed a precociously efficient chewing mechanism, it wasn't as effective as that
achieved by more advanced mammals.
Skull
Before anything was known about the head, docodonts were thought to be fairly derived.
Haldanodon arrived and begged to differ. There are
(Kemp 2005, p.149): "relatively large articular and quadrate bones and also stapes, a
large orbital fissure, which is the space anterior to the
spiterygoid and posterior to the interorbital septum, and a relatively large
septomaxilla bone in the snout." These features
were old fashioned.
Looking out for the kids
The following is based upon my reading of Averianov, 2004, and thanks are due to
the supplier.
The first docodont to be named was Docodon
itself by Marsh in 1891 (p.1). All remains -bits of jaw and isolated teeth- then
came from the Morrison Formation of North America and, had the order been established
at the time, then its sole member would've remained lonely for decades. However, as
nobody saw any reason to even name such an order until after World War Two, then
perhaps this genus didn't appreciate its solitude. The again, this lack of
realization robbed it of joy when the rocks of Dorset's Isle of Pubeck, England
provided a lower jaw as the basis for a further docodont, a birth assisted by GG
Simpson in 1928. This was Peraiocynodon, but it
came with a snag. Suspicions abounded that the new arrival wasn't an adult with
its permanent molars. While there were four
molariform teeth, the opinion was voiced that these were deciduous premolars.
Rather than representing a new genus, it could've been a docodont kid.
Adult docodont lower molars have a cusp termed g located
lingually of cusp a (p.3). This isn't found on
deciduous premolars, tetth that initially performed molariform duties. It's also
absent for Peraiocynodon and, it turned out, for the later described
Cyrtlatherium. Although cusp g is relatively
small for Docodon and Haldanodon, when
compared to Simpsonodon,
Krusatodon or Tegotherium, the cusp is
nevertheless present.
Peraiocynodon inexpectatus may indeed be a juvenile of Docodon, some
traces of which were eventually found in the Purbecks. However, as the amount and
quality of the available specimens from there are presently very limited, this
question is still open.
Moving to the Middle Jurassic Forest Marble of Oxfordshire, this formation has
provided two docodont 'taxa' of which the 'molars' also lack cusp g. Therefore,
they could also be deciduous premolars. The single tooth known as Cyrtlatherium
could've been lost be a young Simpsondon. This had been discounted on the
grounds of its small size and narrowness. However, the difference in size happens
to involve comparing a deciduous premolars with molars of the genus, rather than
with premolars. Various other cited distinctions could be due to the teeth
being primary rather than secondary.
The second relevant taxon is Peraiocynodon major. This could be the very
young form of Krusatodon, also a comparatively large docodont found at the
same locality (p.4).
Euroamericans
As with their Asian cousins, the lower molars of Kursatodon and Simpsonodon
are graced with things called 'pseudotalonid'
basins towards the front. As well as being an impressively strange word, that's a
kind of grinding surface for the upper molar to use. It has been thought that this
similarity could've resulted from sharing a common ancestor with such things.
However, a construction difference suggests not. With the Oxfordians, the front
wall of that basin is provided by a crest running between cusps b and g. That happens
to be reduced in Asian docodonts. Instead, a similar job is performed by two
crests; b-e and e-g.
Link:
Toby White, Palaeos, Mammaliformes: Docodonta
http://www.palaeos.com/Vertebrates/Units/Unit420/420.200.html
A lot of dental detail in a few words. Part of an enormous project which has grown beyond
its initially extremely ambitious intentions.
Genera: Acuoldulodon,
Borealestes,
Castorocauda, Cyrtlatherium,
Dicrocynodon (= Docodon), Diplocynodon (= Docodon),
Docodon, Dryolestes (partly = Docodon),
Dsungarodon, Ennacodon (= Docodon),
Enneodon (= Docodon), Gondtherium,
Haldanodon,
Itatodon, Krusatodon,
Peraiocynodon, Reigitherium,
Sibirotherium, Simpsonodon,
Tashkumyrodon, Tegotherium,
other reports
Time-Line:
Upper Cretaceous: Reigitherium
Lower Cretaceous: Castorocauda, Docodon (Dorset), Peraiocynodon (Dorset),
Sibirotherium, Höövör
Upper Jurassic: Acuodulodon, Docodon, Dsungarodon,
Haldanodon, Peraiocynodon (Wyoming?), Tegotherium
Middle Jurassic: Borealestes, Cyrtlatherium, Gondtherium,
Itatodon, Krusatodon, Peraiocynodon (Oxfordshire), Simpsonodon,
Tashkumyrodon, Siberia (see other reports) |
| Genus: Acuodulodon
Hu Y-M, Meng J & Clark JM, 2007
Remarks: A copy of the description would receive a good home, should anybody have a
copy they could forward. |
| Species: | Acuodulodon sunae Hu, Meng & Clark, 2007 |
| Place: | Shishugou Formation, Junggar Basin, Xinjiang |
| Country: | China |
| Age: | Oxfordian, Upper Jurassic |
| Remarks: | I've seen the abstract of the paper (thanks go
to Jerry Harris for posting it), and it leaves me puzzled. It appears to have been
attacked by gremlins armed with at least one typo: "The new mammal is typical of
docodonts in having a cusp b in front of cusp a, a cusp c distolingual to cusp a and a
cusp g mesiolingual to cusp a on lower molariforms. Differing from other docodonts, it
has no cusp a or crest b-a developed on lower molariforms."
Those sentences are arguing with one another, and the second one's obviously gone barking
mad. Cusp b is found in front of cusp a, but cusp a isn't present! As cusps a, b, c
and g are all mentioned in the rest of the abstract, my suspicions are that cusp e could
be the absentee. Unfortunately, not having a copy of the study means I'm only guessing.
A docodont lower molar without a cusp a would be utterly baffling.
Sadly, the gremlin attack makes me feel the abstract isn't necessarily safe. It also
refers to something termed "a monophyletic dade". What a shame they didn't go for
'monophyletic dad'. |
| Reference: | Hu, Meng & Clark (2007), A new Late Jurassic docodont
(Mammalia) from northeastern Xinjiang, China, Vertebrata PalAsiatica, 45(3),
p.173-194 |
| Genus: Borealestes Waldman M &
Savage RJG, 1972
'northern brigand'
Family: Docodontidae
Remarks: Various translations are available for the Greek word lestes, with
'brigand' being the one specified in the original paper.
Reportedly, a partial skeleton of this animal has been hanging around somewhere
since the 1970s, but it hasn't yet been described, (Martin & Averianov, 2004). |
| Species: | Borealestes serendipitus Waldman M & Savage RJG, 1972 |
| Place: | Kilmaluag Formation, Isle of Skye &
Kirtlington, Oxfordshire |
| Country: | Scotland & England |
| Age: | Bathonian (mid - late), Middle Jurassic |
| Remarks: | The following is based largely upon my reading
of Waldman & Savage, 1972, and thanks are due to the supplier.
Surprisingly to me, I appear to understand the original diagnosis for this mammal (p.122).
The molars have a large main cusp and a prominent cusp on
the lingual cingulum.
Further cingular cusps occur on both sides at the front, and a weak one occupies the
rear of the lingual cingulum. It was very brief as descriptions go.
The jaw fragment featured contains tow and a bit premolars,
four molars, an unerupted fifth and an
alveolus for a sixth. The demarcation between both
types of postcanine teeth is particularly clear from the lingual perspective (p.123).
The premolars are much simpler in build on that side. Their outline does a fair
impersonation of the shape of a pointed woolly hat. Molars are much cuspier. A further
piece of jaw was also available and, if I remember correctly, a partial skeleton turned
up later. Quite surprisingly, that still awaits description 35 years after the launch
of this genus.
Doing a quickie
The presented description was brief as preparation work hadn't been completed (p.124) and,
as far as I'm aware -rather far as it happens, a fuller one is still awaited by an eager
public. Information on dental formula wasn't available beyond there being at least three
premolars and six molars. Premolars have a main cusp, a small cuspule at the rear and
well developed cingula to the fore, rear and buccal
side.
Molars can be more exciting. The largest cusp, a, is tall and situated buccally. A
cingulum cusp, g, is the second largest on the tooth. It's lingual of a and a bit
behind it. A crest connects g with cusp d, found at the rear of the cingulum. Cusp b
is towards the front of the buccal surface of the crown and, forwards and lingual of it
comes cusp h. A hollow area between a-b-h presumably provided services for an upper
molar cusp to go to work with.
Preserved premolars are much the same size as each other. In contrast, the molars
become somewhat larger from m1 to m3, and then decrease in length. There's little trace
of wear on the teeth of the type fossil, and this may indicate a Jimmy Dean docodont;
live fast and die young. The latter suggestion is better evidenced than the first
version.
The jaw bone's a shallow one and has a Meckelian groove
extending forwards to beneath the second molar.
Sizing up
A table provides a summary of tooth dimensions: premolars (two present): both 1.0mm
long, 0.5 wide; molars (four): 1.2-1.4mm long, 0.7-0.9 wide. For the preserved molars,
in contrast to their lengths, the teeth become progressively wider from front to rear.
Affinities
Similarities were found to be strongest with what was then an officially unnamed
docodont from Portugal. Informally, it was called
Haldanodon. These days, it's allowed to wear the name with honour as it's
been legalized.
Holotype
The type fossil, BRSUG 20570, is a student of Bristol University. It's a left lower jaw,
with two premolars and four molars preserved, and its original catalogue number was
UBGM 20570. The specific name refers to its pleasing and unexpected discovery.
Additional notes
A further lower jaw's also known. A number of teeth from Kirtlington are members of the
collection of the Natural History Museum in London. Several are possibly milk teeth.
The revised diagnosis offered by Sigogneau-Russell, 2003, (p.357)
states that the lower molars of this genus are most similar
to those known from Haldanodon. However, the cusps on the internal side
(lingual) in the case of B. are somewhat better
developed, and the lower premolar structure differs.
Eleven teeth or tooth fragments from Oxfordshire have been referred to this species,
(p.361). These specimens show a degree of variability in details of structure, but so does
the holotype.
The type fossil, BRSUG 20570, is a student of Bristol University. It's a left lower jaw,
with two premolars and four molars preserved. A further lower jaw's also known. A number
of teeth from Kirtlington are members of the collection of the Natural History Museum in
London. Several are possibly milk teeth. |
| Reference: | Waldman & Savage (1972), The first Jurassic mammal from
Scotland. Journal of the Geological Society of London, 128, p.119-125. (Source information
kindly supplied by Susan E Evans of the University College of London.) |
| Species: | Borealestes mussetti
Sigogneau-Russell D, 2003 |
| Place: | Forest Marble,
Oxfordshire |
| Country: | England |
| Age: | Bathonian, Middle Jurassic |
| Remarks: |
The following is based upon my reading of Sigogneau-Russell, 2003.
The most readily comprehensible difference between these species, is that B. mussetti
is somewhat larger, (p.358). Other differences are far more technical (and more
significant). In this species, the antero-basal crest is either very weak or absent, the
mesio-lingual cusp is more developed, and so forth. This is dental detail which is hard
for non-specialists to get their teeth into.
According to page 358, the holotype is MNHN J.495, which is a typo. It should read BMNH
J.495 as in the rest of the paper, (with thanks to Dr Sigogneau-Russell for kindly
confirming this). The specific name honours Dr Frances Mussett for major participation in
the collection of the Kirtlington fossil fauna. |
| Reference: | Sigogneau-Russell (2003), Docodonts from the British Mesozoic.
Acta Palaeontologica Polonica 48(3), p.357-374. |
| Genus: Castorocauda
Ji Q, Luo Z-X, Yuan C-X & Tabrum AR, 2006
'Beaver tail'
Remarks: The following has been contributed by somebody writing in the year 2106. As I'm
informed that's a hundred years in the future, I'm astonished at the speed of e-mail.
A future correspondent writes
If you'd care to consult any recent book concerning Mesozoic mammals, then you'll see how
monumental were the advances prompted by discoveries dating from the previous century.
Indeed, prior to the 21st century serious researchers even spoke and wrote about mammals
having existed in 'the shadow of the dinosaurs'. Although it might seem laughable to us
now, they seemed to be of the opinion that Mesozoic mammals had little better to do than
hide, or occasionally sneak out for a bit of insect, worm or plant! I'm sure many of them
knew this was a pale reflection of former realities but, when it came to the broader
picture, mammals were restricted to, at best, the sidelines. Many books concerned with
terrestrial vertebrates didn't mention mammals at
all!
Improved vision
Today, if you access the Kids' Section of a BookMarkt, you'll find plenty of well-written
and lavishly illustrated books on Mesozoic Mammals. Equivalent products from the 1900s
seem strangely obsessed with dinosaurs. Let me stress,
this isn't because those authors were blind. They simply had very little to look at.
No reasonably complete specimens were seen until the 1990s, and researchers thought
themselves lucky if they chanced upon half a skull. You frequently find more informative
mammalian specimens in breakfast cereal packets than pre-21st century paleontologists had
available. A few fossils began to change this in the late 20th century, but it wasn't until
the new millennium that this trickle turned into a torrent.
The finest find of the last century
The previous 100 years produced so many magnificent specimens, that no two judges are likely
to agree on their personal top five, and nor will there be consensus on the winner. Even if
we restrict ourselves to the first decade, I'm not sure which fossil I'd pick as my personal
favourite. For example, how could I exclude the dino diet of
Repenomamus? I suppose I could snub it on the grounds of a complete lack of
fur, but it would be fairly prudish. A better reason would be the necessity of choosing
both the hairy therians;
Eomaia and Sinodelphys. Should you
prefer audacious specialisation, then you could select the anteating
Fruitafossor, but it would surely lose
out in most people's eyes if compared with the excellent
Castorocauda which, when discovered, wore the oldest directly evidenced fur coat
and webbed feet ever seen, as they dated back to before 125 million years.
There are other excellent candidates I could mention, but the length of the list wouldn't
help me reach a decision. And that's only taking the first decade of the last century into
account.
The 21st century was when Mesozoic mammals really began to roar and, fairly soon, even the
entertainment industry couldn't ignore them. For example, the only mammals featured in the
first ten Jurassic Park films were human actors, and the last of those was so badly
received that many thought it would literally be the last. However, a radical re-write
resulted in Castorocauda being given the central role, and the series hasn't looked
back since. |
| Species: | Castorocauda lutrasimilis Ji Q, Luo Z-X, Yuan C-X
& Tabrum AR, 2006 |
| Place: | Daohugou Locality, Jiulongshan Formation, Inner Mongolia |
| Country: | China |
| Age: | ?Middle Jurassic |
| Remarks: | The following is based upon my reading of Ji et al,
2006, and my thanks go to Jeff.
Reasons to be cheerful
I'm going to start of with a short list of novelties which make Castorocauda a stonk
of a stunner, and I could have added more.
# Previously, Mesozoic mammals preserved to this degree of excellence all came from the
The Yixian Formation, Liaoning. This is from a different
Formation and age.
# It adds millions of years to the direct evidence of fur coats.
# Prior to this publication, it had been inferred that basal
mammals kept some middle ear bones on their jaws. This was on account of scars and
roughened attachment surfaces, as the bones themselves were tiny, fragile and loosely
attached. Those attachment areas can't be seen on this fossil because the bones are in
place. The articular /
malleus, the angular /
ectotympanic and a surangular bone are all present.
# This is the most complete Jurassic mammal ever seen. (Correction: The age of this
location isn't yet fully clear, but present betting makes Lower Cretaceous the
favourite.)
# This is twice the size of any other docodont.
# This is the biggest Jurassic mammal ever seen (although not by all that much, as the
reported fifty centimetre length includes twenty centimetres of tail - and it seems
to be Cretaceous).
# That tail contains precisely 25 vertebrae, and they're
all still in place.
# Webbed feet!
# The 'platypus style' tarsal spur on the ankle is kicked deeply back towards the roots of
the mammalian family bush.
That's nine clear reasons for being stunned and, when typing this introduction, I've only
had a brief read of the description. However, I can't resist adding one more point to the
list.
# If there's one mammalian corpse in this former lake, then there are almost certainly
more.
(Update: That justification is bang on.
Volaticotherium glided in at the end of 2006, and it's another absolute
stonker. Is it a bird? Is it a glider? No, it's Volaticotherium flinging
itself from tree to tree.)
'Beaver tail'
Castorocauda is clearly a semiaquatic docodont. Such a tendency was already strongly
suspected for one relative (Haldanodon), but this new
addition is better preserved and undoubtedly more specialised for a watery way of life. It's
also considerably larger and some teeth suggest a fondness for fish.
Neighbours and size
This mammal was naturally part of a community, and other local residents have been
identified (p.1123). Among them are pterosaurs, a
coelurosaur dinosaur, amphibians, lots of insects and
other invertebrates.
The complete length of 'beaver tail' would've been about 50cm, but 40% was provided by the
tail. If we lop that portion off, then what remains is a critter a bit bigger than large
rats. No Jurassic
mammals as large had previously been found, although (if regarded as a mammal) some
representatives of Sinoconodon probably
managed 25cm (as opposed to 30).
Nature of the beast
Its affinities are clear from the rear molars, as these have
docodont crowns. The lower dental formula is (per side): 4
incisors, 1 canine, 5
premolars and 6 molars. Of the latter, m3 to m6 possess the necessary qualifications
for Docodonta. There's a large cusp g to the front on the
lingual side; triangulated crests are formed by ridges connecting cusps a-c and a-g;
cusps also provide two partly enclosed basins. The traditional form of mammalian molars
produced shearing teeth, but docodonts had developed effective grinding mechanisms in
addition.
Front molars
The first two molars are a different kettle of fish. These are essentially like the
traditional mammalian model, but with some refinement. The crown has a straight line of
cusps running centrally from front to back. In this instance there are five. The central
cusp (a) and its two followers (c and d) curve somewhat inwards at their tips. These teeth
mimic 'triconodont' molars, and no docodont has previously been caught wearing anything
like them.
However, they do resemble the content of much more recent
placental mouths; mesonychians, Eocene whales and some seals. This seems to be
convergence due to similar tastes; fish.
Where to find middle ear bones
I don't know if you happen to be unusual in this respect, but I keep my middle ear bones in
my ear. Castorocauda was normal enough as well in its
basal mammalian way, as it stored middle ear bones on the lower jaw. If you'd care to
take a close look, you should be able to see I've got three very small ossicles in my ear
for processing sound. There's an incus, a
malleus and a stapes, and
they're ably supported by a further bone called the
ectotympanic. The same bones were involved with hearing for Castorocauda, but
only the stapes was in the ear. This may sound odd but it all makes sense in terms of the
evolutionary history.
Middle ear bones have to be small, or else they wouldn't fit in. They were small, fragile
and loosely connected when mammals used to keep them on the jaw. It was clear enough that's
what was being done, as the attachment apparatus was well known. The bones themselves,
however, were never preserved. 'Beaver tail' made sure to take greater care, and these
elements are still in place. Achieving this through such a length of time is
astonishing.
Relativity
Middle ear bones being located on the dentary is a feature
in common with non-mammalian eucynodonts and early
mammals (p.1124). In the terminology of the paper,
docodonts are confirmed as being mammaliaforms.
However, they are further derived than
morganucodontids. Doubts about that have
sometimes been expressed in the past. Within Docodonta, the closest known relatives of
this genus seem to be Krusatodon and
Simpsonodon. Both come from roughly similarly aged deposits in England.
The oldest fur coat in the world
There's good reason for believing hair predates Mammalia, and evidence points to Lower
Triassic Thrinaxodon as probably hairy.
This evidence is indirect. Fur is a terrible candidate for fossilisation. Nevertheless,
should conditions be bizarre enough, it can occur. At the start of this millennium, the
oldest directly evidenced mammalian hair belonged to a 60 million year old called
Lambdopsalis. The owner had been eaten, and
various bits of the body (including hairs) were found inside fossilised droppings.
This was spectacularly topped by a variety of 125 million year old Yixian Formation
mammals, with Eomaia at the head of the fashion
parade in 2002. 'Beaver tail' ups the stakes further. It also places directly
evidenced hair on a critter, which is undoubtedly outside of
crown-group Mammalia. The fur was already
differentiated. A thicker coat was next to the skin, and guard hairs stuck out from it for
protection and (presumably) tactile information gathering.
Tail
In contrast to the Yixian specimens, the tail of
Castorocauda was furry, but there are also traces of carbonised scales (p.1125).
Ask a mouse for further details of scales on mammalian tails. The distribution of fur and
scales in this case is reminiscent of the beaver, thus 'beaver tail'. The front quarter
has plenty of guard hairs. These are much sparser on the middle portion, which was mainly
scaled. The final quarter is more of a cocktail (in a manner of speaking). Added to this
is the broadness of the vertebrae, bones which have
characteristics in common with both beavers and otters. This tail is suitable for plenty
of water sports.
Legs
Both Castorocauda and the aforementioned Haldanodon have front limb features
in common with Ornithorhynchus, aka the
platypus, and these point towards digging (p.1126). This is reflected in all the available
bones which, in the case of Castro, include the toe bones. These are wide and robust.
The limbs are also well suited for swimming. The back feet even show traces of soft tissue
between the toes, and these indicate webbing.
The ankle has something of interest as well. This is a projection at the back called the
tarsal spur, and it's known from extant monotremes and
various Mesozoic mammals. The male platypus uses this as a venom delivery apparatus. It
hadn't previously been found with a docodont, but that applies for the whole ankle. As
well as monotremes and a docodont, evidence of this tarsal spur has now been gathered for
some multituberculates,
'symmetrodonts' and triconodonts. It was recently
suggested this could indicate a widespread use of venom among ancient mammals. I'm
sceptical as to that possibility. More can be read in:
Of spurs and venom.
Spine
The count had to be estimated, as part of the body is missing. (The plate's incomplete.)
The probable numbers were 14 thoracic, 7
lumbar and 25 caudal
vertebrae. Somewhat unexpectedly, the thoracic and lumbar spine bones have
costal plates; extensions which overlap with the neighbouring
bones. This is unusual for mammals although it occurs in a less developed way with
Repenomamus. Narrower versions are also
favoured by extant, placental xenarthrans (eg. anteaters). They presumably strengthened
the trunk of the body and serve (in xenarthrans) as adaptations helpful for digging and
climbing.
Mammalian heavyweight
Admittedly, there were some larger animals around, but not many
furry ones. (At least, not furry mammals. Some non-mammalian
tritylodontids are known to have been bigger. There's no direct evidence of hair on
tritys, but it's difficult to believe they could've been nudists.)
The size of this individual falls within the range for female platypussies (39 - 55cm), and
a mass range for a sample of these animals recorded weights of 700 - 2400 grammes. A
number of theoretical masses were calculated for Castorocauda based on different body parts.
The results fell between 500 to 800 grammes. If the platy comparison is appropriate, then
700 would be conservative.
Holotype
The type fossil, JZMP 04-117, is a resident of the Jinzhou Museum of Paleontology. The
specific name translates as 'otter-like' (Latin).
Additional notes
Dating and Updating
The Supplementary information for the description justifies the age. Castorocauda
was retrieved from Bed 3 of the Formation, which is 20 metres below a horizon featuring
volcanic ash. This was radiometrically dated by two methods (40Ar/39Ar and 206Pb/238U).
These gave results of 164.2±2.5Ma and 164.6±2.4Ma respectively.
However, the justification seems to have been wrong. The problem is that this bed
is apparently above the volcanic ash, and not below it. Consequently, it's younger.
The age is presently thought to be somewhere between 165 million and 125 million
years, with bets accumulating for the more recent end of the range. The matter isn't
yet settled, and the critter may be Upper Jurassic. According to the original
authors it was Middle Jurassic, but that's apparently questionable. |
| Reference: | Ji, Luo, Yuan & Tabrum (2006), A swimming mammaliaform
from the Middle Jurassic and ecomorphological diversification of early mammals, Science,
311, p.1123-1127. |
| Genus: Cyrtlatherium
Freeman EF, 1979
'Cyrtian beast'
Remarks: The genus was originally referred to
Kuehneotheriidae, but it's now thought to be based on docodont teeth, and is perhaps
synonymous with Simpsonodon.
'Cyrtia' is an Anglo-Saxon proper noun and is responsible for the place name of
Kirtlington. |
| Species: | Cyrtlatherium canei Freeman EF, 1979 |
| Place: | Forest Marble,
Oxfordshire |
| Country: | England |
| Age: | Bathonian, Middle Jurassic |
| Remarks: | The following is based upon my reading of Freeman,
1979.
As the sole specimen was described as a kuehneotheriid, some of the terminology used could
be inappropriate. For that reason, I'll add inverted commas. The language used for teeth
of differing groups of mammals isn't always the same. While cusps may perhaps occur in
broadly similar areas of a tooth, these structures aren't always homologues with those of
distantly related mammals.
Freeman described Cyrtlatherium lower molars as having
'recurved protoconids', which were less robust than the (not necessarily) corresponding
structure in Kuehneotherium (p.146). A
cingulum on the lingual
edge curves up from beneath the 'protoconid'.
Two teeth (and a third possible) were referred to the taxon:
both lower molars. The type fossil was the more complete (p.148), as it had lost only the
ends of the roots. The 'protoconid' was described as being considerably taller than both
the 'metaconid' and 'paraconid', with the latter cusp aligned with the 'protoconid'. That
particular arrangement would've been odd. True
paraconids are habitually lingual of
protoconids.
A distinct crest runs between the 'proto-' and 'paraconids' on the lingual side. The whole
length of the crown is blessed with a cingulum. This curls round at both the front and rear
of the molar, but then fades away. This cingulum has an accessory cusp at the back of it,
but none to the front.
Size
The length of the type fossil is 0.83mm and its maximum width is 0.37.
Holotype
This is a right lower molar, which the author had catalogued as FM/K 11. As Freeman donated
many specimens to the Natural History Museum, it's since become BMNH 36511. A lot of
effort can be required for finding fossils, and the generosity of many collectors is
laudable. Unusual specimens are often freely given to accessible collections simply for
the advancement of knowledge. The specific name honours Derek J Cane. He both found the type
fossil and did much work in support of the study.
Additional notes
No further specimens have since been found at Kirtlington, (whether published or otherwise),
which leaves Cyrtlatherium feeling a bit underrepresented (Sigogneau-Russell, 2003,
p.359).
It may be that the known fossils are milk teeth, (p.363). Working on that assumption,
Sigogneau-Russell discusses the possible affinities. For reasons including size,
Borealestes seems a strong candidate. However, the absence of an antero-
lingual crest seems to rule out B. serendipitus,
whilst it doesn't compare closely enough with a possible milk tooth of B. mussetti.
She notes similarities with Simpsonodon: "However, as long as no docodont d/2
is better known, it will be hazardous to confirm or reject this proposed synonymy, though
it remains likely that Cyrtlatherium is based on a
deciduous tooth.". (The following links include an abstract by Averianov, 2004.
According to that, Simpsonodon is a junior synonym of
this species.)
Maschenko et al, 2002 (p.79) suggests it may by synonymous with
Simpsonodon. |
| Reference: | Freeman (1979), A middle Jurassic mammal bed from Oxfordshire.
Palaeontology 22, p.136-166. |
| Links:
Acta Paleontologica Polonica 46(3)
http://www.paleo.pan.pl/acta/acta46-3.htm
Sigogneau-Russell D (2001), Docodont nature of Cyrtlatherium, an upper Bathonian
mammal from England, p.427-430.
Palaeontology 22
http://palaeontology.palass-pubs.org/pdf/Vol%2022/Pages%20135-166.pdf
Freeman, 1979 is presently freely accessible in pdf format.
Russian J. Theriol. Vol.3. No.1: 1–4
http://www.orc.ru/~kmkweb/abstracts/averianov2.htm
Averianov AO (2004), Interpretation of the Early Cretaceous mammal Peraiocynodon
(Docodonta) and taxonomy of some British Mesozoic docodonts - The Abstract.
"Interpretation of the dentition in the holotype of Peraiocynodon inexpectatus
Simpson, 1928 as d1–4 (Butler, 1939) is confirmed. Two taxa of docodonts from the British
Middle Jurassic are based on the lower milk teeth: Cyrtlatherium canei and
Peraiocynodon major. Simpsonodon oxfordensis Kermack et al., 1987 is a junior
subjective synonym of Cyrtlatherium canei Freeman, 1979 (syn. nov.) and
Peraiocynodon major Sigogneau-Russell, 2003 is a junior subjective synonym of
Krusatodon kirtlingtonensis Sigogneau-Russell, 2003 (syn. nov.)."
I think I'll await confirmation of the confirmation, especially as I haven't seen the
paper. |
Genus: Docodon Marsh OC, 1881
'beam tooth'
Aka: Dicrocynodon Osborn, 1888 ("From Marsh (MS)",
McKenna & Bell, 1997); Diplocynodon 'double dog tooth', Marsh, 1880;
Dryolestes Marsh, 1879 (partly); Ennacodon Marsh, 1890; Enneodon
Marsh, 1887; Peraiocynodon Simpson, 1928
Family:Docodontidae Simpson, 1929
Remarks: Most known material was collected for Marsh in 1879 -1881. Diplocynodon
Pomel, 1847 is a crocodile genus.
The reassigned species from the Morrison Formation haven't been formally synonymized with
D. victor. However, Martin & Foster, 1998 (p.384): "Therefore, although a
formal synonymy has not been undertaken, the consensus suggests that all Docodon
species from Como Bluff may represent D. victor (Marsh, 1880)." I'm presently
assumingly they are the same species, though I have left entries for two of the possible
taxa for which I have some specific information.
| Reassigned species: D. affinis see D. victor; D.
crassus see D. victor | |
| Species: | Docodon striatus Marsh OC, 1881 |
| Aka: | Dicrocynodon striatus |
| Place: | Morrison Formation, Wyoming |
| Country: | USA |
| Age: | Upper Jurassic |
| Remarks: |
A further specimen of this species was recovered from Mammal
Quarry, in the Black Hills of Wyoming. It was described by Martin & Foster, 1998 and
the following is my interpretation of their presentation. This specimen is in the
collection of the South Dakota School of Mines and Technology. It's a partial lower jaw
with about one and a half molars in situ, and has a
length of about 3cm.
From page 388: "The dentary exhibits fine striae
subparallel to the distinct internal groove. This feature is identical to that of the type
specimen of Docodon striatus, YPM 11823, and was the basis for the specific name.
Simpson (1929, p. 94) attributed this feature to poor ossification of a juvenile dentary.
The preserved molar of SDSM 26911 is almost unworn, and the anterior portion of the
internal groove is exceedingly faint, features suggestive of a young individual and
reinforcing the contention of Simpson."
As these authors represent the opinion that all the Morrison species probably are one and
the same, they refer this fossil specifically to D. victor, which seems very
reasonable in the circumstances. Should anyone by wondering, striae refers to scratches
or stripes. |
| Reference: | Marsh (1881), New Jurassic mammals. American Journal of Science,
Series 3 (21), p.511-513. |
| Species: | Docodon superus (Marsh, 1880) Simpson, 1929 |
| Aka: | Dicrocynodon victor (Marsh, 1880) Marsh in Osborn, 1888 |
| Place: | Morrison Formation, Wyoming |
| Country: | USA |
| Age: | Upper Jurassic |
| Remarks: |
Simpson meant this species name: "as a blanket term for all specimens possessing upper
dentition", (Martin & Foster 1998, p.384 -I think
'known from upper dentition would've been a tidier phrase). It's likely synonymous with
D. victor, though it hasn't (as of 1998) been formally referred to that species,
which is based on lower teeth and jaw material. |
| Reference: | Simpson (1929), American Mesozoic Mammalia. Memoirs of the
Peabody Museum, 3, p.1-171. |
| Species: | Docodon victor (Marsh, 1880) Simpson, 1929 |
| Aka: | Dicrocynodon victor; Diplocynodon victor Marsh, 1880;
Docodon affinis; D. crassus |
| Place: | Morrison Formation, Wyoming |
| Country: | USA |
| Age: | Upper Jurassic |
| Remarks: |
It could be that all the Morrison Formation D. fossils
belong to the same species. If so, this is the one. It's presently based upon lower
teeth.
"The occurrence of the genus Docodon in the Black Hills is interesting, as this
taxon is known only from two other localities: Garden Park,
Colorado, and Como Bluff, Wyoming. Sites at Dinosaur National Monument and Fruita have
produced numbers of well-preserved multituberculates
and dryolestids but no docodonts. The apparent
restriction of Docodon to eastern quarries may represent a paleobiogeographic
pattern", Martin & Foster 1998, p.390).
John H Burkitt lists this species as being known from the Upper Jurassic of Europe. The
above paragraph suggests that's incorrect. Then again, Machenko et al, 2002 (p.79) states
Docodon is known from the Early Cretaceous of Europe. The Purbeck Limestone of
Dorset sometimes gets referred to as Upper Jurassic and Lower Cretaceous. |
| References: | Marsh (1880), Notice of Jurassic mammals representing two new orders. Am. J. Sci. (3) xx, p.235-239. |
| Simpson (1929), American Mesozoic Mammalia. Memoirs of the
Peabody Museum, 3, p.1-171. |
| Species: | Docodon sp. |
| Place: | Purbeck Limestone Group, Dorset |
| Country: | England |
| Age: | Berriasian, Lower Cretaceous |
| Remarks: |
Some material is in the collection of The County Museum, Dorchester. It's not sufficiently
well-preserved to be assigned to a species, whether new or established. |
| Reference: | |
| Genus: Dsungarodon
Pfretzschner H-U & Martin T, 2005 in Pfretzschner H-U, Martin T, Maisch MW, Matzke AT
& Sun GE, 2005
'Dsungar tooth'
Remarks: Although the paper has five authors, both the genus and species are attributed to
only two of them. As that's what's written on pages 800 and 802, I assume it's what was
intended. The Junggar Basin was previously transcribed as the Dsungar Basin. However, it
changed its name upon marriage, and Chinese custom is to cite the family name first. (Part
of that sentence is ever so slightly untrue.) |
| Species: | Dsungarodon zuoi Pfretzschner H-U & Martin T,
2005 in Pfretzschner H-U, Martin T, Maisch MW, Matzke AT & Sun GE, 2005 |
| Place: | upper Qigu Formation, Junggar Basin, Inner Mongolia |
| Country: | China |
| Age: | Oxfordian, Upper Jurassic |
| Remarks: | The following is based upon my reading of
Pfretzschner et al, 2005.
The Junggar Basin is in northwest China, and several localities there have attracted
research workers from a joint Chinese-German project. As I'm English and start discussing
the weather at any opportunity, (it's all we ever talk about), I can divulge some inside
information given to me in the strictest confidence. The fieldwork occurred during the
summers, and might have appealed to some who like it very hot indeed. One of the locations
sampled was part of the Upper Jurassic (Oxfordian) Qingu Formation (p.799), and it was kind
enough to produce teeth and a couple of small bits of jaw from a docodont. This might be
termed a contrary sort of critter, as it has characteristics more in keeping with Middle
Jurassic Britons than its known Asiatic colleagues, but no mammal has ever been allowed to
choose its relatives. Lucky ones do get to have a say in making descendants.
A lower molar feature termed a
"pseudotalonid" and a couple of enlarged
cusps distinguish newly described Dsungarodon from the
Haldanodon - Docodon area of the order; animals
which belong to a more basal lineage. An unusual
characteristic is that the teeth have well developed grinding abilities, which point to
different dietary preferences. This suggests 'Dsungar tooth' had more of an interest in the
plant life; an omnivorous or possibly herbivorous lifestyle.
A brief history of Asiatic Docodom
Until the 1990s, the known history of docodonts was restricted to North America and Europe,
but Tegotherium managed to change that. It was
originally thought to be an odd 'symmetrodont', but
then squeaked out a demand from Asia: 'Let me in!'. Docodont admirers were glad to oblige.
A further candidate emerged from the Middle Jurassic Balabansai Formation of Kyrgyzstan.
Unfortunately, the poor condition leaves this as no more than a possible. A
'Haldanodon-grade' lower molar from the Indian Kota Formation still waits patiently
for description. Relatively generous has been Shestakovo in Siberia, which has so far
come up with three partial dentaries from
Sibirotherium. That locality is notable for several
surprisingly late representatives of eucynodont
lineages. This applies to docodonts and non-mammalian
tritylodontids. The most recently published docodont prior to Dsungarodon was
Tashkumyrodon from the Middle Jurassic of Kyrgyzstan.
Liuhuanggou in the Junggar Basin
The Basin has an impressive collection of sedimentary rocks, as deposition was underway from
the Permian until the Upper Cretaceous. The amalgamated thickness amounts to around
16,000 metres, 6,000 of which built up thanks to the efforts of rivers and lakes. Several
parts of the Toutunhue Formation (Middle Jurassic, Callovian) and the overlying lower
Qigu Formation are fossil rich. The Qigu has a thickness of around 730 metres at the
Liuhuanggou site, and its Upper Jurassic age was established by studies of spores and
polynomorphs.
The relevant bonebed in this case is 470 metres above the boundary between both Formations,
and was found in 2000 (p.800). It's come up with an interesting mix of
vertebrates including hybodontid sharks,
temnospondyle amphibians, turtles,
crocodiles,
dinosaurs and (according to the text!) both 'haramyids'
[sp.] and docodonts. (Apart from the slight misspelling, the only local 'haramiyid' so
far described is from a different and earlier bonebed. I wonder if a slip of the keyboard
might have allowed Eleutherodon to sneak
into the wrong bed.)
A Dsungarodon inventory
The type fossil is a single molar in a fragment of jaw, but it does enjoy some company.
There are four further lower teeth, (including a couple of milk
premolars), and an upper molar. To the naked eye, the entire ensemble could look like
a few largish grains of sand, so it's a blessing microscopes are available.
Upper molar comparisons
Various characteristics suggest this genus is more
derived than the somewhat later Portuguese docodont called Haldanodon. Among
these is the presence of a basin, formed by crests connecting cusps termed A, C, Y
and X. The molar has more resemblance to
Simpsonodon from the Middle Jurassic. Differences from
that taxon include cusps A and C on the
buccal side of the crown. In Dsungarodon, these are
more slender, and they're much taller than X and Y on the
lingual side. The lingual portion of the tooth is relatively reduced, and the whole
crown is more triangular in shape. The outline bears some similarity to a rather crumpled,
irregular heart.
Lower comparisons
Cusps and crests of lower molars form a basin at the front of the crown; a
"pseudotalonid". The details of this terminology are somewhat tricky. Firstly,
a talonid is a basin found at the rear of
tribosphenic molars. The anterior position in this
case disqualifies that term from applying. The quotation marks are significant, as they
denote a difference to the genuine pseudotalonid found
on teeth of a non-docodont called Shuotherium.
A broadly similar structure developed several times during mammalian history.
Be that as it may, Dsungarodon's "pseudotalonid" contrasts with the
structure found in its Asiatic docodont colleagues, (Tegotherium, Sibirotherium
and Tashkumyrodon), in that the cusp termed e doesn't form part of the basin wall
(p.801). The crown in the new genus also possesses a more old fashioned trait. There's a
well developed crest connecting cusp b with g.
This "pseudotalonid" isn't part of the more basal
furnishings found on the molars of Haldanodon or Docodon. Other relatively
derived characters include a reduced cusp f and crest c-d, while cusp b is enlarged and
cusps c and g are about the same height.
Some readers may be relieved to learn that a quiz on these details isn't part of the
schedule. If you fear your score would've been nought out of ten, you've got nothing to be
ashamed of.
A brief tour of the upper molar
SGP 23 is a specimen from the right tooth row and probably one of the middle molars (p.802).
There were three cusps on the buccal side, (B, A and C from
front to back), but B is no longer in residence. A is a bit higher than C. Two cusps are
located on the lingual part of the crown. Of these, X is
larger than Y. Cusps A and C are both about twice the height of X. All cusps are convex
on the lingual face and concave on the opposite one.
There are a number of crests connecting the various cusps with one another. The details are
in the description and a link can be found below. Suffice it here to say that various wear
facets are available, and provide information on how this tooth interacted with its lower
partner. The authors also draw attention to a: "wide buccal shelf with a strongly
developed ectoflexus." As they term this 'a
striking characteristic', I thought I'd mention it.
Lower milk teeth
There are a pair of fragmentary, left, deciduous
premolars. These are described as molariform, (ie.
molar-like), but they're comparatively narrower and longer than molars. Deciduous premolars
are often more complexly constructed than their replacements, and this reflects growth
patterns. As more jaw grows, space becomes available for further choppers. However, biting
power always remains strongest nearest the skull-jaw joint, and this means the tooth
positions best supplied will change with age until adulthood. In young mammals, premolars
may be doing work which is later the duty of molars.
Lower permanent premolar
Given the information in the preceding paragraph, the adult version is relatively shorter
and broader than the juvenile premolars. One specimen has been identified and it was
double-rooted, although only the rear one remains. The referral of this fossil to the
genus is actually tentative.
Lower molars
There's a bit more from the lower jaw than just teeth, as two
molars (including the holotype) are preserved in small fragments of bone. The type
fossil certainly isn't the ultimate tooth from the series, as part of an
alveolus for a further tooth is behind it. As with the
premolar, this tooth is also double-rooted, and it overhangs the
mandible it's adorning, as it's wider. There are five cusps: a, b, c, d and g. That
begs a question about e and f. These are present on some docodonts molars, but not in the
case of Dsungarodon. Cusp a dominates with b being the second tallest and g the
lowest. Various cusps and crests contribute to the previously mentioned
"pseudotalonid" basin. A particularly well developed crest runs from b to g and
provides part of the wall of the basin, as is the case for earlier English critters;
Simpsonodon and
Krusatodon.
Lower jaw
A second specimen, SGP 22, also comes with some jaw, and kindly adds several further details.
Preserved is the front of the postdentary trough and the beginnings of a
Meckelian groove. These are both archaic features for
mammals, and they're located on the inner side of the
dentary. I wouldn't be seen dead with either. As the coronoid process begins its
ascent close behind the tooth, this molar must be the last team member of the
dentition. The molar is smaller and simpler than the
holotype. For example, only cusps a, b and g could be found.
Are these isolated teeth from the same set?
The uppers and lowers have features and wear facets which complement one another in
exquisite detail, and are docodontan. As an example: "As docodonts are the only known
mammals with an occlusal mode where the
"pseudoprotocone" (cusp X) fits lingually to the
corresponding lower molars producing buccally facing wear
facets (numbers 5, 6 and 7 in docodonts after Crompton and Jenkins 1968; Butler 1997), the
attribution of upper molar SGP 23 to Docodonta (and Dsungarodon) is justified."
Arguments are presented for referring all fossils to the same
taxon, with the proviso concerning the tentative attribution of the permanent premolar.
The short answer to the above question is: more or less yes (but not necessarily from one
mouth).
Relationships
The authors interviewed ten genera about their lower molars; nine docodonts and a possible
early relative called Woutersia. Questions were limited to
a set of seven traits (p.805). 'Dsungar tooth' provided answers most similar to those given
by Simpsonodon and, to a lesser degree, Krusatodon. Common characters uniting
D. and S. include: the reduction of both cusp c and crest c-d; the loss of f;
the similar sizes of c and g; and the "pseudotalonid". In contrast, K.
retains e as a distinct cusp and f at the back.
This albeit limited data set suggests Tegotherium is more
closely related with this trio than are other tegotheriids. If so, then the present
composition of that family falls into some disrepute. It would be rendered
paraphyletic (bad) instead of
monophyletic (good). It wouldn't be a proper
family.
What's for dinner?
The authors provide an analysis of the chewing techniques of the genus, in as far as
isolated teeth and comparisons with other sources allow. As the available details include
wear facets, a fair amount is known about how uppers and lowers cooperated. They point out
that the specialisations evident for both Dsungarodon and Simpsonodon allow
for enhanced grinding abilities (p.807). This would be useful for breaking down foodstuffs
such as plants and worms. Armoured insects request a pointier, more cutting approach, as
armour needs to be pierced. That indicates that these two docodonts (and the tegotheriids)
were equipped to tackle a wider menu, than was the case for less
derived relatives such as Docodon. Orders placed in the
restaurant could have involved tasty salads. Grinding functions are best developed in
'Simpson's tooth' and 'Dsungar tooth'.
Holotype
The holotype, SGP 21, is a right lower molar (length 1.49mm, width 0.95mm). It presently
resides at the University of Tübingen in Germany. After completion of its studies, the
tooth plans to return to China with its colleagues, but it hasn't yet decided which
institution to apply to. The specific name honours Professor Zuo Xue-Yi. As the then
director of the Xinjiang Geological Survey No. 1, he was able to provide much support for
the fieldwork. |
| Reference: | Pfretzschner et al (2005), A new docodont mammal from the Late
Jurassic of the Junggar Basin in northwest China, Acta Palaeontologica Polonica, 50(4),
p.799-808. |
| Genus: Gondtherium
Prasad GVR & Manhas BK, 2007
'Gond beast'
Family: Docodontidae Simpson, 1929
Remarks: The generic name honours the Gond tribe, members of which live in the area
of the fossil locality. Despite what you might think, it isn't a truncated
reference to Gondwana, so there! |
| Species: | Gondtherium dattai Prasad GVR & Manhas
BK, 2007 |
| Place: | Kota Formation |
| Country: | India |
| Age: | ?Middle Jurassic |
| Remarks: | Traditionally, there's been a tendency to
stamp 'Lower Jurassic' on anything coming out of this Formation. However, at least
in part, remains may be more recent, and suggestions of age even extend as far as
Lower Cretaceous. I've tentatively opted for Middle Jurassic. Prasad & Manhas
don't. I'm not advocating this age as being 'correct'. Rather, I've got no
particular view on the matter, no qualifications but have to write something!
The following is based upon my reading of Prasad & Manhas, 2007.
The presence of a docodont in Central India's Kota Formation has been known about
for some years, but a formal description somehow seemed to reluctant to show itself
in the light of day. Unfortunately, this study includes reference to the loss of
the longed for molar, and that may help account for
the delay. However, although less informative in accordance with their simpler
nature, an upper premolar announced itself
agreeable to becoming the type fossil of a new genus, Gondtherium. It was
itself first mentioned in print in 1999, so it's had some experience of life as a
minor celebrity, and it was felt capable of dealing with the role given the absence
of the envisaged star performer. And so it left the now entirely depopulated
chorus line, and took up its position beneath the spotlights at stage centre.
(That's theatre-speak. I've trodden the boards professionally myself, you know. I
think I was paid a hefty £1.15 per hour in 1982, and shared the headlines with Ella
Fitzgerald. Admittedly, she was in the other auditorium on the Wednesday evening,
but that's mere detail.)
Setting up the scenery
The stage set shows the upper reaches of the Kota Formation as portrayed by a
stream cutting close to the village of Paikasigudem (p.1). The age this play takes
place in is rather less clear than it previously seemed. New studies have sometimes
produced more uncertainty. The lower member has provided dinosaurs (Barapasaurus
and Kotasaurus), mammals (Kotatherium
and Indotherium) and fossilized wood
samples. Being upper, the upper member is somewhat younger. How much so is
debatable. Prasad & Manhas opt for Middle Jurassic to Lower Cretaceous.
The upper vertebrate fauna is more varied (p.2)).
Fish, in the broadest common usage of the term, include semionotids, pholidophorids,
freshwater sharks and a coelacanth. Some kind of frog sometimes popped its head out
of the water, perhaps to watch the turtles and crocs at play. More terrestrial
activities were pursued by dinos (theropods and
ornithischians), lizard-like sphenodontids, and
a lizard-like lizard. Pterosaurs patrolled the skies. And, as the main tourist
attractions, mammals did their utmost to slaughter the creepy-crawlies.
Gondtherium is the fifth from this fauna. It joins
Trishulotherium,
Nakunodon,
Paikasigudodon and Dyskritodon.
Not yet described is a possible dryolestoid
known from two premolars.
Several of those fish were accused of pointing their fins towards a Lower Jurassic
age. However, ostracods from the upper fauna (the same member as the fish) were
heard shouting Middle Jurassic. That's partly consistent with recent palynological
data suggestive of between uppermost Middle Jurassic to Lower Cretaceous. I can't
see any of this provides grounds for considering the lower fauna also to be Middle
Jurassic, but there might be reasons I'm ignorant of. The presence of prosauropods
is more in line with Lower Jurassic for that.
Taking the stage
The new star is an upper left premolar identified
as a P3, the final one of a series (p.3). The tooth has an asymmetrical, triangular
outline, an impressive width, and three main cusps; two
buccal, one lingual. These are separated by a
basin. Two buccal cuspules at the front help to differentiate it from the corresponding
tooth of Haldanodon and
Docodon superus. There are also differences concerning the degree of
development on the lingual side. It compares most closely with the first mentioned
genus. However, possibilities for direct comparisons are limited as this is a
premolar, and such teeth are unknown for a considerable proportion of other
docodonts.
A star portrait
The fault may lie with my understanding, but I can't reconcile the measurements
mentioned with the line drawings in Figure 2. The sketch shows the front of the
tooth is considerably narrower than the rear, and that's how come the outline is
kind of triangular with the hypotenuse built be the lingual side. The buccal side
is nearer to being horizontal. However, the stated figures seem to tell me the
maximum width is 50% greater anteriorly than posteriorly, and I can't see how that's
possible. The width more or less continuously diminishes from back to front.
A line of three cusps runs along the buccal side with the largest, A, positioned in
about the middle. It's twice the height of C to the rear. A small cuspule to the
fore is presumably a reduced cusp B (p.4). Slightly forward and lingual from that
occurs cuspule E. Returning attentions to the back of the tooth, there's a large
and long cusp named X on the opposite side from C.
Crests run from A to C and A to B, and another connects B with E. A crest also
descends lingually from A, although wear obscures its original destination; perhaps
to X. Presumably, if the enamel had also been preserved, then such details would
have been somewhat clearer. However, the enamel's gone, and that makes me wonder if
the former owner may have been severely bullied with a one-way tour through
somebody's guts. For example, the digestive juices favoured by crocs do tooth
enamel more harm than treacle toffee. Be that as it may, A and X are on the opposing
banks of a deep basin. Further crests link X with C and also X with E. If all
that's a bit hard to digest, then you've come to a reasonable conclusion through
your confusion; this premolar has a complex crown.
Any wear facets that may have been present departed with the enamel. The roots have
also long since gone, but traces suggest there was a trio of them.
Compared with other performers
Two large buccal cusps, the asymmetrical outline, the wide basin between A and X and
a pinch in the crown lingual from those cusps are badges of pride worn by docodont
upper postcanines (p.6), and especially the
premolars. That narrowed possible comparisons down to only Haldanodon and
Docodon. The A cusp is larger for D. superus, C is much smaller and
both B and E are tiny. The X has partly split in that species to produce an
accessory cusp.
Further such comparisons are executed for Haldanodon and various docodont
molars. To be brief, the authors found this fossil most closely resembled the P3
of Haldan, and that suggests it's from a similar dental position; the final
premolar (p.7).
There are two factors not in line with other docodonts, but both could be matters of
preservation and/or tooth type. The accessory cusp of X (known as Y) isn't present,
but it doesn't always occur on premolars, and its absence could be the result of
slight chipping. Secondly, a crest linking A and X would be expected. When unworn,
one may have been present.
The wider cast
The present state of play indicates two divergent branches of the docodont dynasty;
a western empire -which may have included Rome- in Europe and North America, and an
eastern empire with not even Byzantine connections to Constantinople, as far as is
known. Asian docodonts have now been caught loitering in various parts of that
continent. It's possible that a couple of Euro taxa
could be phylogenticly Asian by descent. However, all members of both lots are
northerners; Laurasian. Gondtherium is a Gondwanan, and died at a time when
India had nothing whatsoever to do with Asia. Should docodonts have played
football, and there's no evidence showing they didn't, then the Indian team would
have most likely been affiliated with the Confederation of African Football.
While the closest similarities with Haldanodon may indicate ties with the
Euroamerican wing, such an assumption could presently be no better than tentative.
Resemblances with Asian premolars might be even more striking, or less. As no
asiadocodontan specimens are yet available, it would be a matter of comparing like
with nothing whatsoever (p.8). Gondtherium does demonstrate Gondwanan
docodonts existed. However, assuming Reigitherium
from Argentina isn't a remarkably late docodont, a single premolar is the sum total
of things from the entire southern hemisphere Mesozoic. The authors do refer it to
Docodontidae, but further discoveries could easily demand revision of that. Time
will tell.
Holotype
VPL/Ju/KM/12 is an upper premolar attending lectures at the University of Jammu,
India. The specific name is for PM Datta, the Director of the Geological Survey of
India. He was the first person to describe a mammal from the Kota Formation. |
| Reference: | Prasad GVR & Manhas BK (2007), A new docodont mammal
from the Jurassic Kota Formation of India, Palaeontologica Electronica, 10,
p.1-11. |
| Genus: Haldanodon Kühne
& Krusat, 1972
Family: Docodontidae Simpson, 1929
Remarks: "Nomen nudum in Kühne, 1968," (McKenna & Bell, 1997). |
| Species: | Haldanodon exspectatus Kühne WG & Krusat G, 1972 |
| Place: | Guimarota |
| Country: | Portugal |
| Age: | Kimmeridgian (middle), Upper Jurassic |
| Remarks: | The following is based upon my reading of Martin &
Nowotny, 2000
Leaving the disputed Reigitherium out of the equation,
the fossil record of docodonts presently extends from the Middle Jurassic to the Lower
Cretaceous, and across all three continents of the northern hemisphere. That's something like
fifty million years of time and a lot of land. However, with the exception of finds from
one location, virtually nothing is known beyond fragments of jaw and teeth. Haldanodon
is that exception. Over two hundred bits of jaw, (152 lower and 67 upper), have been
recovered from Guimarota, and that would be sufficient for the status of best represented
genus. In this case, they happen to be accompanied by ten more or less complete skulls,
(p.91). None have turned up anywhere else. Rather than resting on its fully merited laurels,
this disused coalmine even provided a partial skeleton. This is unique for docodonts.
While teeth provide important information on affinities, they can't say all that much about
appearance and lifestyle, except for giving some idea of size and possible diet. Sometimes,
mammalogists can be accused of being obsessed with teeth, but that's often the only
information available.
Of a docodont and moles
In this instance, it's beyond doubt that Haldanodon was about the size of a mole,
and they're much smaller than they sometimes look in cartoons; perhaps up to about fifteen
centimetres in length. As it happens, the upper limb bones have something of a mole-like
aura. Both the femur and humerus
are strongly built bones with massive, broad ends. This provides plenty of room for the
attachment of muscles, which allow the wherewithal for a life in the worm mines.
Lifestyle
The postcranial bones available are well preserved. Among living mammals, the desman of
Europe shows strong similarities. These are semiaquatic mole relatives, with one genus in
Spain and another in the Volga area of Russia. They're burrowers who patrol the banks of
rivers and streams, and do their best to control the population levels of snails and
insects. The feet and tail of desmans are specialised for swimming. These body areas
aren't known for Haldanodon, so whether similarities went as far can't be said.
However, the flattened shaft and impressive crest for anchoring muscles on the humerus
speak eloquently about digging.
In moles, the humerus is even wider; the maximum width and length are close. The length
clearly wins for the docodont. Given that the remains were found in a Jurassic swamp, a
semiaquatic animal with adaptations for burrowing is highly plausible, (p.92). Real moles
prefer drier ground.
Skull
On skull has a length of 3.8cm and the bones are unusually thick, (p.93). The
nasals are shields covering the front half of the head.
There's also evidence consistent with a further specialised feature on the forehead, where
the bone features roughened areas. This isn't likely to have been for a miner's helmet
with a lamp, but a keratin shield would be a good explanation.
The back of the skull is relatively high, so the head is shaped something like a wedge when
viewed from the side. There's also room to accommodate strong neck muscles. Existing
golden moles, (which live much like moles but aren't closely related), are similar in this
respect. They use their heads to shovel already loosened dirt out the way.
Dental hygiene
Dentists would frown if examining Haldanodon, but they hadn't been invented in the
Upper Jurassic. The molars are often severely worn. While
being nutritious, worms and grubs come supplied with soil and sand. They're both yummy and
abrasive. Modern river bank mammals have a similar problem. Kids, it's not just sugar
that can damage your teeth. If you must eat worms, make sure you purge them first.
Teeth
The molars of docodonts are complicated constructions, and clearly not
derived from ancestors with tiangulated
trigonids. This alone suggests the group is a
basal branch of the mammalian bush. The upper molars are
particularly wide, and that characteristic was the basis for the name. Docodont means
'beam tooth'. It also increased the area available for food processing, which allowed an
advance in crushing abilities. However, the jaw mechanics dictated movement was relatively
restricted, (p.94). Without a freer mechanism, there was a limit to the enhancement of
chewing efficiency.
The dental formula per side reveals an unusual predilection for
incisors, which is perhaps a primitive trait: (uppers): six incisors, one
canine, three premolars and
five molars; (lowers): four, one, three and five to six
respectively. Despite some variability in numbers of lower molars, all remains are of the
same species.
The wide sample of jaws available makes it clear that tooth replacement was
diphyodont; teeth were replaced only once. As with
modern mammals, molars seem to have been permanent. Replacement of premolars began at the
front and proceeded along the line, although the third
deciduous one was retained for somewhat longer than might be expected, (p.96). In one
lower jaw, it's still in place with five fully erupted molars. The lower canine was
replaced after p2, while the upper emerged before P2. As is usual, replacement teeth are
less complex than the first series. As the jaw bones lengthen with age, the bite power
remains concentrated nearest the jaw joint. This reality of biomechanics dictates the area
where chewing can be most effective; at the back of the tooth row.
Making whoopee
No sexual dimorphic characteristics have been identified, so differentiating between males
and females is presently impossible. The presence of seventeen jaws with partially
preserved milk dentitions, (p.95), indicates that the
animals themselves were far more adept in this area of research than the paleontologists
are. They could obviously make this diagnosis, and presumably derived much satisfaction as
a consequence.
How old fashioned!
Originally, when the remains of docodonts were very restricted indeed, the complex molars
led to the conclusion that these animals were probably relatively close relatives of
therians, (in a wide sense of the word). However, while the teeth were
derived, they were very differently derived. Better
material showed they were also housed on primitive jaws.
All existing mammals have only a
dentary-squamosal mandible-cranium joint. Haldanodon maintained the archaic
articular-quadrate one as well, albeit in a
hardly functional form, (p.96). Small 'extra' bones were stored on the back of the jaw in
the end of the Meckelian groove; a further feature
not associated with any mature, modern mammals. These bones were loosely attached, but the
corresponding marks on the dentary attest to their presence
in life.
As the articular and quadrate are the origins of the mammalian
malleus and incus respectively, their lingering presence
on the jaw implies there could only have been one sound processing bone in the middle ear,
(the stapes). This was confirmed by an analysis of the
skull.
Holotype
The holotype is VJ 1001-155. My thanks go to Father Christmas for supplying the study
from which this information is drawn.
Additional notes
I've seen this genus referred to on a webpage as an Early Jurassic morganucodontid, which
is not correct.
Ears
Unusually for docodonts, the inner ear of this genus is preserved to some extent and it
shows an interesting feature. As reported on p.91 of Luo, 2001 (see Bibliography):
"The cochlear canal does not extend the entire
length of the pars cochlearis in Yunnanodon,
thus resembling those of Sinoconodon and
Haldanodon, in the proportion of the cochlear canal to the pars cochlearis."
In all other critters that are as, or more 'mammalian'
than Morganucodon, that's not the case.
This feature, microscopic though it be, could provide support for the emergence of
docodonts from 'pre'-morganucodontid-grade ancestors. Then again, there could be another
explanation. Will somebody please find some more docodont ears?
Updates on the body
The following is based upon my reading of Martin, 2005.
This paper was the first detailed description of the postcranial remains of a docodont.
The skull and teeth had already been treated, but the body of Haldanodon had required
patience; rather a lot, considering the partial skeleton was discovered in 1979 (p.219).
As the docodont awaited these attentions, it was joined by further isolated bones from the
same genus. Given that this was only the second Jurassic mammal to have provided significant
parts of its skull and skeleton in clear association (the first was
Henkelotherium), this may sound somewhat
sedate. However, it took time for the fossil to be prepared. Besides, what's a quarter of
a century in comparison to 153 million years?
The study adds a great enrichment of detail, but it doesn't do a lot to alter the image
sketched previously; a desman-like swamp dweller. Should anybody be thirsty for those details,
a link to the paper is below.
If you've got it, flaunt it
The star specimen is the partial skeleton, and this was found in a lump of coal. It was
decided to preserve as much of the fossil as possible in its original configuration (p.220).
The matrix on one side was removed and then replaced by transparent resin. A similar
procedure was then followed for the other side, and the result would make a fascinating,
see-through paperweight. In a few instances, the coal proved uncooperative so some elements
are now isolated. A couple of dozen bones from other animals complete the available
collection. Should anybody desire an even more gloriously naked docodont body, then
Castorocauda subsequently performed an astonishingly
evocative striptease in 2006. That's good enough to turn even committed eunuchs randy.
Gui Mam 30/79 consists of much of the skull, parts of its seductive shoulders, alluring
limbs, bits of ribs and pieces of fingers or toes. Reportedly, isolated carpals and tarsals
were also present. However, Martin couldn't identify them. The other specimens add various
body parts to the scene, notably the pelvis.
An arms race
The most numerously represented single bone is the humerus
of the upper arm, for which seven specimens are available. A surprising aspect is the range
of lengths; 11.8mm to an estimated 18.5 (p.221). This is rather extreme.
Although the sample size for the femur is but two, the same
theme is reflected in the leg. One femur has a length of 14.4mm and the second 20.0. The
partial skeleton happens to represent one of the smaller critters. However, as it already
had five molars on the upper right jaw, it can't have died at all too young an age (p.222).
It would be interesting to have information on comparative jaw lengths, should anybody have
some available.
"The humerus of Gui Mam 30/79... is short and robust and is even stronger and thicker
than the femur of the same individual" (p.226, figure reference omitted). I don't
know about you, but my upper leg is considerably thicker than my arm. The reverse applies
to the bones of this docodont. The front legs were well muscled and powerful and, when it
comes to moving from place to place, only some acrobatic humans use their front legs for
much propulsion. The duties of front legs in locomotion mainly concern balance and weight
support. Arms like this are made for digging.
Size variation
There's no compelling indication among the remains of any more than one species of docodont
in the fauna, and that suggests a different explanation is required for the size differences
of morphologically similar bones. One possibility is an unusually prolonged period of
growth (p.228). Martin even points to the chance of lifelong growth. This would be very
odd for a mammal (living versions don't do that sort of thing), but there is a long dead
precedent; Sinoconodon. That earlier genus was
at least a near-as-damn-it mammal.
I'm left wondering whether it could be a matter of sex, which is a subject that frequently
comes to my mind. This possibility isn't addressed for some (perhaps very good) reason.
Different species could be a further explanation, but that wouldn't be in line with the
similar morphology. |
| Reference: | Kühne & Krusat (1972), Legalisierung des taxon
Haldonodon (Mammalia, Docodonta). Neues Jahrbuch für Geologie, Paläontologie and
Mineralogie, Monatshefte 5, p.300-302. |
| Links:
Senckenberg Museum, Zoological Journal of the Linnaen Society, 2005
http://www.senckenberg.de/files/content/forschung/abteilung/terrzool/mammalogie/postcranial_anatomy_of_haldanodon_expectatus_from_the_late_jurassic_of_portugal.pdf
Thomas Martin's study is presently freely accessible on line. The url is impressively
long.
Pressestelle FU Berlin
http://www.fu-berlin.de/presse/fup/archiv/pdw00/pdw_00_031.html
A press release, (in German), concerning the Guimarota fossil site, where various mammal
fossils have been found.
Der Tagesspiegel, Berlin, Nr.17 294, 18.1.2001, p.29
http://www.pfeil-verlag.de/07pala/e2_80r3.html
A press report on Haldanodon and friends from Guimarota. For non-German speakers,
there's an illustration and a photo of the jaw. |
| Genus: Itatodon
Lopatin AV & Averianov AO, 2005
'Itat tooth'
Family: Tegotheriidae Tatarinov LP, 1994
Remarks: The generic name reflects glory on the Itat Formation, the rocks of which
were kind enough to provide the fossil. |
| Species: | Itatodon tatarinovi Lopatin AV & Averianov
AO, 2005 |
| Place: | Berezovsk quarry, Itat Formation, Siberia |
| Country: | Russia |
| Age: | Bathonian, Middle Jurassic |
| Remarks: | The following is based upon my reading of
Lopatin & Averianov, 2005. This is the English language translation, rather than
the original Russian description from earlier in the same year. Details are in the
bibliography at the foot of this page, and thanks are due to the kindly supplier.
Docodonts used to be known as an obscure group of Mesozoic mammals boasting a handful
of genera from North America and Europe. Over the last few years, they've moved into
Asia and are breeding rampantly. One Chinese specimen went beyond anybody's wildest
hopes by continuing to sport its furry coat and webbed feet:
Castorocauda, the finest fossil of the entire 21st century. A year prior
to the debut of that spectacular superstar, an earlier and more modest member crept
into print from a Middle Jurassic quarry in Siberia. So quiet was its squeaky song,
that some people completely failed to hear of it. For example, there was me. I
didn't get to appreciate any of its music until the abstract of a more expansive
paper on Itatodon came my way late during 2006. As it's now two years after
the birth of this no longer so new arrival (written in March, 2007), I hope these
much belated greeting won't be seen as a sign of disrespect.
Berezovsk rocks
Docodonts were announced as present in this Middle Jurassic quarry before the
description of Itatodon, but that news concerned toothless jaws. This specimen
is a jawless tooth (p.434). Features of the lower molar
crown show its owner to have been a member of an increasingly extended family, the
Asiatic tegotheriids. Derived traits include: a
"pseudotalonid" enclosed within a quartet of
crests running between the various cusps, a-b, b-e, e-g and a-g; the top of the cusp
a points somewhat backwards; cusp c and the rear part of the crown are both reduced;
the presence of a complete cingulid on the buccal side
of the crown and a partial one towards the front of the
lingual margin (at the level between cusps a and b); several details concerning
positions of crests. Basal characters include the absence
of a cusp termed ee, and the lack of crenulation in the enamel.
One is the loneliest number...
As this is based on an isolated molar, assessing its precise location in the tooth
row is problematical, especially given the absence of information from any other
individuals. Docodonts are known to have possessed between five and eight of these
teeth per side, and this presumably had one or other of those numbers. As it's a
proportionately long tooth, the rear two positions are unlikely. Other details
could perhaps prove helpful but, given that the new genus also had its own specialisations,
which could be informative as to its position in the row would perhaps become
clearer from a wider sample. For example, the crest termed a-g has a notch in the
middle and, in conjunction with the posterior inclination of the a cups, this seems
to be an analogue of a meat-cutter found on the teeth of extant carnivorans and
others (p.435). The owner was something of a butcher.
Age
Being from the Middle Jurassic, this in one of the earlier of docodonts. Nevertheless,
its molar exhibits a series of specialisations that required time to be developed.
That suggests a long docodont chain of ancestors going back for many generations,
and perhaps with its roots in the ancient soils from before the Middle Jurassic.
"Pseudotalonid"
It's a lovely word, isn't it? This thrilling sounding feature is a basin positioned
mainly on the lingual half of the front of the crown. As indicated above, it's
enclosed by crests running between a number of cusps. The cusp known as a is the
largest one on the tooth, and it has its peak well back behind the halfway line of
the crown. A crest connects its front lower slope with cusp b, and that's situated
further towards the front of the crown on the lingual
area. A further crest runs from it to cusp e, a small prominence on the anterior
buccal corner. The second tallest molar cusp is known
to its friends as g, and it's roughly about halfway between e and a, but a bit further
buccal than either of them. A crest connects e with g, a furthered notched one links
g with a, and this basin is enclosed by all those crests. In effect, this basin
has similarities with a structure found on the lower teeth of far more advanced
mammals, the basined talonid. However, that's found
at the back, this is to the front and is thus a "pseudotalonid".
If that's still a bit of a struggle to grasp, then stop worrying about the funny
words and letters. Let's be straightforward. This is a very complex bit of natural
engineering in a relatively early mammal.
Roots
There's one at the front and a snapped off partner at the back. Both are narrow,
long and slightly curved. The front root was probably a bit longer.
Measurements
While the animal must've been small, it can't have been counted among the smallest
fry of Middle Jurassic Mammalia (p.436). The molar
has a length of 2.1mm, a maximum width of 1.2 and the highest point of cusp a
attains 1.6. Root depth mines down to 2mm. As some kind of vague, insecure guess
based on merely a single tooth, I'd be inclined to think more towards rat- than
mouse-sized. However, that's very vague indeed.
Congratulations
While not being the first Middle Jurassic mammal fossil described from Russia,
Itatodon is the winner when it comes to having been named. And, to give full
credit to the Berezovsk quarry for making this possible, its local fauna can now
boast of more named Middle Jurassic mammalian taxa
than the entire continent of North America. The village of Nikol'skoe 1
USA-Canada-Mexico 0. For reasons of avoiding embarrassment at international
conferences and other social events, it's clearly essential for the heads of those
states to be hanged...
...in shame, and for them to make the search for Middle Jurassic mammal fossils an
urgent priority.
Holotype
PIN 5087/2 is a lower right molar now imprisoned at the Paleontological Institute,
Saint Petersburg. The specific name honours LP Tatarinov: "... who described the
first docodont from Asia." This is true, although he didn't originally describe
it as a docodont.
Additional comments
A further paper by Averianov and Lopatin appeared in 2006 and, certainly in terms
of length, it's more extensive. It hasn't been taken into account above, as I haven't
yet read it. For many people, it'll prove easier to get hold of: Averianov & Lopatin
(2006), Itatodon tatarinovi (Tegotheriidae, Mammalia), a docodont from the
Middle Jurassic of Western Siberia and phylogenetic analysis of Docodonta, Paeleontological
Journal, 40(6), p.81-90. At some stage, further information from that will appear
here.
At the end of this section, the 'Other Reports'
contain information on the locality and some of its fossils. These include two bits
of toothless docodont jaw which, judging by the abstract of the 2006 study,
don't seem to have been assigned to this taxon. At
least, it's stated that the genus: "is represented by two lower molars and a lower
molar fragment...", and nothing else is mentioned.
Cheers
Thanks are due to Jerry D Harris for posting notification of the 2006 publication
(and the abstract) to the Dinosaur Mailing List (17.12.2006). |
| Reference: | Lopatin AV & Averianov AO (2005), [A new docodont
(Docodonta, Mammalia) from the Middle Jurassic of Siberia], Doklady Akademi Nauk,
405(2), p.277-279 [Russian language]. |
| Genus: Krusatodon
Sigogneau-Russell D, 2003
'Krusat's tooth' |
| Species: | Krusatodon kirtlingtonensis Sigogneau-Russell D,
2003 |
| Place: | Forest Marble,
Oxfordshire |
| Country: | England |
| Age: | Bathonian, Middle Jurassic |
| Remarks: | The following is based upon my reading of
Sigogneau-Russell, 2003.
"Lower molars differ from those of all other docodont genera (?except Tegotherium
Tatarinov 1974) by the depth of the lingual and distal furrows of the main cusp, and by the
posterior crest of the talonid, which bears there cuspules", (p.359). It may perhaps
be synonymous with Tegotherium. However, strong doubts have since been expressed.
[From Martin & Averianov, 2004: "We have no space here to discuss the taxonomy
and relationships of the new British docodonts in details, but wish to point out that
Krusatodon is similar to Simpsonodon and differs from Tegotherium and
Tashkumyrodon gen. nov. by retention of a complete crest b-g and therefore belongs
to the Euroamerican clade of Docodonta."]
These molars are relatively large, (p.361). The main cusp is
crossed by ribs and deeply furrowed. Two cusps on the lingual
side are well developed. Several basins are present; both a
talonid and a 'pseudo-talonid'.
Holotype
The holotype is a right lower molar, affectionately known as BMNH J.526. It's an inmate
of the Natural History Museum in London, and serving time with about half-a-dozen other
specimens, including a milktooth or two. The generic name's in honour of the late Dr
George Krusat, and his important work on docodonts. The specific name is geographically
derived. |
| Reference: | Sigogneau-Russell (2003), Docodonts from the British Mesozoic.
Acta Palaeontologica Polonica 48(3), p.357-374. |
| Genus: Peraiocynodon
Simpson GG, 1928
Remarks: This genus may represent juvenile Docodon material, (milk teeth).
That would make it junior synonym of Docodon, or a similar critter. However, this
is not certain, and a further species has been described in 2003.
Family: Docodontidae |
| Species: | Peraiocynodon sp. |
| Place: | Morrison Formation, Wyoming |
| Country: | USA |
| Age: | Upper Jurassic |
| Remarks: | I have not yet found a specific reference to this
material, but I'm assured it exists. |
| Reference: | |
| Species: | Peraiocynodon inexpectatus, Simpson GG, 1928 |
| Place: | Purbeck Limestone Group, Durlston Bay, Dorset |
| Country: | England |
| Age: | Berriasian (early), Lower Cretaceous |
| Remarks: |
This genus was revised by Sigogneau-Russell, 2003, on the basis
of some new material. "Differs from all other genera by the relative narrowness of the
lower molars and the development and detachment of the
disto-labial cusp (labial
talonid cusp)", (p.359).
The lower molars of this particular species are: "characterised by small size, a marked
anterior indentation, the presence of an antero-basal crest and of a
lingual ridge.
The holotype, BMNH M 48348, is part of a left dentary
described as possessing two premolars and two molars.
However, whether that's what the teeth are has been questioned. On page 370: "As for
the type jaw of P. inexpectatus, it should be interpreted as bearing one definitive
molar and three deciduous premolars, as suggested by
Krusat (1980): the latter are much more molariform than are the definitive premolars of
Docodon for instance."
It's in the collection of the Natural History Museum, London, in the company of some
colleagues. Further specimens are housed in The County Museum, Dorchester. |
| Reference: | Simpson (1928), A Catalogue of the Mesozoic Mammalia in the
Geological Department of the British Museum, London, p.1-215. |
| Link:
Ian West, Durlston Bay pages
http://www.soton.ac.uk/~imw/durlston.htm#correl
This site includes a useful index of three extensive articles on the geology and
paleontology of Durlston Bay, Dorset. This is a very thorough piece of work. I think it's
great. |
| Species: | Peraiocynodon major, Sigogneau-Russell D, 2003 |
| Place: | Forest Marble,
Oxfordshire |
| Country: | England |
| Age: | Bathonian, Middle Jurassic |
| Remarks: | Update:
Averianov, 2004 found this species to be a jurnior synonym of Krusatodon
kirtlingtonensis. The abstract is in the links following
Cyrtlatherium.
The following is based upon my reading of Sigogneau-Russell, 2003.
This species is much larger than P. inexpectatus, and much earlier. The front of
the teeth are also narrower, and they lack both an antero-basal crest and a
lingual ridge. They differ in several other details too,
(p.359).
The two teeth referred to this taxon show some unusual details, as reported on pages
361-362. Several possibilities were considered for their diagnosis, (p.363). They were
ruled out as representing the milk dentition of the relatively large genus,
Krusatodon, nor do they seem to be its premolars.
Nor do they appear to be the deciduous molars of
Docodon. Sigogneau-Russell found a striking resemblance to the smaller choppers of
Peraiocynodon inexpectatus, thus the establishment of this second species. She
points to a number of common, seemingly derived characters: "(great development of the
disto-labial cusp, absence of mesio-lingual cusp, ornamentation and concavity of the
distal face, disto-lingual cusp weakly detached) lead to the grouping of these two forms
into one generic unit; which represents a solid argument for keeping the Purbeck taxon
independent from the various species of the genus Docodon", advice which I have
followed here.
Several inconsistencies found their way into this paper. The abstract states, (p.357):
"Peraiocynodon major sp. from Purbeck". In terms of both geology and
geography, this unfortunately indicates Dorset. However, the Systematic paleontology
section correctly cites this material as coming from the Forest Marble of Kirtlington.
The body of the paper carries the intended information, whilst the abstract is incorrect.
(With thanks to Dr Sigogneau-Russell for the confirmation.)
The type fossil is a lower, left molariform tooth, BMNH J.693. Out of a spirit of meanness,
I refuse to explain the derivation of the species name. |
| Reference: | Sigogneau-Russell (2003), Docodonts from the British Mesozoic.
Acta Palaeontologica Polonica 48(3), p.357-374. |
Genus: Reigitherium
Bonaparte JF, 1990
Family: Reigitheriidae Bonaparte JF, 1990
Remarks: If you'd prefer a dryolestoid, an entry based on Bonaparte's original description
is available: Reigitherium as a dryolestoid. |
| Species: | Reigitherium bunodontum Bonaparte JF, 1990 |
| Aka: | Reigitherium bunodonta Bonaparte JF, 1990 (The species name was corrected in accordance with Latin grammar.) |
| Place: | La Alamitos Formation & La Colonia Formation,
Patagonia |
| Country: | Argentina |
| Age: | Campanian-Maastrichtian, Upper Cretaceous |
| Remarks: |
Based on teeth and some dentary material, which was
referred to Docodonta in 2000. I found the idea of an Upper Cretaceous docodont difficult
to believe. But then again, egg-laying mammals surviving until the present day sounds far
fetched too, unless you're a duckbilled platypus. It was previously placed within
Dryolestida, another group more frequently
encountered in the Upper Jurassic of the northern hemisphere.
As with mammals Upper Cretaceous dinosaur taxa from South America also have a tendency to
be apparent late survivors from a previous age, (seen from a northern perspective). This is
a remarkable phenomenon, but there does seem to be a recognisable consistency in play.
(With thanks to David Marjanovic for the discussion.)
The original diagnosis was based upon a single tooth: "Because of its unusually wide
crown, it was logically regarded by Bonaparte (1990) as a left upper
molar," (Pascual et al 2000, p.402). However, the new
specimen showed it to be a lower molar. Reigitherium "shares with the North
American Jurassic genus Docodon several derived
dental features, eg., lower intermolar basins formed by the adjacent halves of molars and
vertical crenulations (or ribs and furrows) on the molar crowns... Additionally, the
presence of the triply-rooted pm4 supports the docodont affinities of
Reigitherium," (Pascual et al 2000, p.405). This latter feature is reportedly
otherwise only known from monotremes.
The docodont affinities of this genus are not universally recognized. Other
interpretations see it as a dryolestoid. |
| Reference: | Bonaparte (1990), New Late Cretaceous mammals from the Los
Alamitos Formation, northern Patagonia. National Geographic Research 6 (1),
p.63-93. |
| Genus: Sibirotherium
Maschenko EN, Lopatin AV & Voronkevich AV, 2002
'Siberian beast'
Family: Tegotheriidae Tatarinov, 1994 |
| Species: | Sibirotherium rossicus Maschenko EN, Lopatin AV
& Voronkevich AV, 2002 |
| Place: | Shestakovo 1, Kemerovo Region |
| Country: | Russia |
| Age: | Lower Cretaceous |
| Remarks: |
The following is based upon my understanding of Maschenko et al, 2002.
The type fossil is part of a left dentary with three teeth
in situ. These are presumably the last two of four
deciduous premolars, and the first
molar, (p.77). All are slightly worn, so they'd been used
for nibbling. This can't have been a baby. In front of the premolars are four holes,
(alveoli). As the teeth present are blessed with two
roots of similar length each, these were probably for the other premolars, (deciduous or
otherwise). The dentary is described as shallow.
The premolar at the front (?dp3) has three main cusps in a line. The middle one is the
tallest and is found in the centre of the crown. The other two are much smaller. ?dp4 is
intermediate in structure between this tooth and the molar, (m1).
m1 has a rectangular crown. Cusp a is large and conical. There are various other cusps
and ridges, and a deep basin at the front, (a
'psedotalonid'). A couple of other jaw fragments preserve further dental details. One
of these suggests there were probably at least six molars in all, (diagram on p.78).
"The structure of the ultimate deciduous premolar of Sibirotherium rossicus gen.
et sp. nov. is similar to that of Docodon ["Peraiocynodon"]
(Butler, 1939) and Haldonodon (Krusat, 1980: figs. 23, 24). However, in comparison
to Docodon, the penultimate deciduous premolar of Sibirotherium gen. nov.
exhibits the more simplified pattern, without cusp c and crest a-c. The two anterior
deciduous premolars are double-rooted, as dp1 and dp2 of Docodon", (p.79).
Home sweet home
The Shestakovo locality was first worked in 1953, when two partial specimens of
Psittacosaurus were recovered. There are several sites close to this village, which
is in the south-east area of the West Siberian plain, (p.75). As yet, there's disagreement
concerning the age of these remains, with estimates ranging from Berriasian-Valanginian
to Aptian-Albian. In either case, this is the latest recorded occurrence of a docodont,
with the possibly spectacular exception of Reigitherium.
The locality has been the subject of intensive excavations conducted largely by teams
from Tomsk University, aided and abetted by further specialists from Moscow and Saint
Petersburg. This work commenced in 1995, which is also when the first mammalian fossils
came to light. Most finds turn up in coarse sands and sandstones. In all, something like
20 vertebrate genera (26 species) have so far been identified; fish, amphibians, a turtle,
lizards, dinosaurs, pterosaurs, birds, mammals and a surprisingly late, non-mammalian
tritylodontid named
Xenocretosuchus, (p.76). The other mammals
are apparently three species of Gobiconodon,
an indeterminate amphilestid, and Kiyatherium.
Holotype
The holotype (pm tsu 16/5-22) resides in the collection of the Paleontological Museum of
Tomsk State University, along with two further dentary fragments. The material was found
by Shikhovtseva LG, Maschenko and Voronkevich in 2000. The species name refers to Russia. |
| Reference: | Maschenko, Lopatin & Voronkevich (2002), A new genus of the
tegotheriid docodonts (Docodonta, Tegotheridae) from the Early Cretaceous of West Siberia.
Russian Journal of Theriology, 1 (2), p.75-81. |
| Genus: Simpsonodon
Kermack et al, 1987
'Simpson's tooth'
Family: Docodontidae
Remarks: Update:
Averianov, 2004 found this species to be a jurnior synonym of Cyrtlatherium canei.
The abstract is in the links following Cyrtlatherium. |
| Species: | Simpsonodon oxfordiensis Kermack KA, Lee AJ, Lees PA & Mussett F, 1987 |
| Place: | Forest Marble,
Oxfordshire |
| Country: | England |
| Age: | Bathonian, Middle Jurassic |
| Remarks: |
Remains include a fragment of lower jaw with two molars
and at one premolar. Other isolated teeth have also been
identified. Thomas & Nowotny 2000, (p.91), rate this as being "very similar"
to Haldanodon. Maschenko et al 2002, (p.76), also point to several details of
dentistry which this genus shared with the tegotheriids. These are listed in the entry for
Tegotherium, (below).
"Docodonts are unusual among Mesozoic mammals in the development of a wear surface on
the mesio-lingual part of the lower molar... In at least one genus, Simpsonodon,
this developed into a basined surface and assumed a grinding function", (Luo et al
2002, p.15). Never mind the anatomical complexities. The point here is that
Simpsonodon could grind its food, which is in contrast to many of its
mammalian contemporaries and predecessors. A similar
capability, via a different dental trick, is known from Shuotherium. Otherwise,
this method of improved nutritional processing seems to be largely restricted to
tribosphenic mammals; lineages which lead to ourselves, kangaroos and duck-billed
platypussies. |
| Reference: | Kermack et al (1987), A new docodont from the Forest Marble.
Zoological Journal of the Linnean Society, 89, p.1-39. |
| Species: | "Simpsonodon splendens" (Nomen nudum) Kühne,
1968 |
| Place: | Guimarota coalmine |
| Country: | Portugal |
| Age: | Kimmeridgian, Upper Jurassic |
| Remarks: | Kühne never published a detailed description under
this name. Later, the material was named Henkelotherium guimarotae Krebs,
1991. It is a paurodontid, not a docodont. (Source: Dr T Martin, Berlin.) |
| Reference: | Kühne (1968), Kimeridge (sic) mammals and their bearing on the
phylogeny of the Mammalia. In Drake E (ed) Evolution and Environment. Yale University
Press, p.109-123. |
| Genus: Tashkumyrodon
Martin T & Averianov AO, 2004
'Tashkumyr tooth'
Family: Tegotheriidae Tatarinov, 1994
The following entry is largely based upon my reading of Martin & Averianov, 2004. My
copy doesn't have the original page numbers.
Tegotheriidae: The Euramerican-Asiatic docodont split
Update: Pfretzschner et al, 2005 suggests the concept of Tegotheriidae may be a
paraphyletic assemblage rather than an actual
family (p.805).
In the opinions of Martin & Averianov, docodonts were the descendents of a
Woutersia-like animal. Its lower
molar would've had a cusp a as the main cusp, cusp c displaced to the
lingual side, cusp b on the
buccal, well-developed cusps e, g and d, and four main connecting ridges, (crests in
the specific terminology employed for docodonts). Further crests and cusp f would've been
added during the 40 million years which separate Woutersia, (not formally placed
within Docodonta), and the earliest known docodont, (
Borealestes). A feature shown by all docodonts, (but not Woutersia), is
a crest a-g. The authors therefore propose this as a unifying characteristic for the order,
(a synapomorphy).
Following the establishment of that crest, Docodonta appears to have split into two main
branches. This could be connected with a geographical development; the separation of Europe
and Asia by the Turgani Strait at various stages between the Middle Jurassic, (Bathonian),
and the Oxfordian stage of the Upper Jurassic.
"All Euramerican docodonts, including Simpsonodon,
are characterized by reduction or loss of cusp e and strong reduction of crest b-e."
Borealestes, Haldanodon and
Docodon appear to be the most conservative. Simpsonodon may have evolved
from something akin to Borealestes. Whilst the presence of a
"pseudontalonid" is a feature that genus
shares with the Asiatic tegotheriids, this differs in its construction and can be accounted
for by convergence rather than common descent.
"The Asian docodonts differ markedly from Euramerican docodonts by retention of
unreduced cusp e, formation of crests b-e and e-g (which are not present in any known
Euramerican docodont) and by subsequent reduction of crest b-g". A remnant of this is
present in Tashkumyrodon, but not in its further
derived colleagues. |
| Species: | Tashkumyrodon desideratus Martin T &
Averianov AO, 2004 |
| Place: | Balabansai Formation, Tashkumyr |
| Country: | Kyrgyzstan |
| Age: | Callovian, Middle Jurassic |
| Remarks: | This fossil comes from a site on the bank of
Sarykamyshsai Creek a few kilometres east from the town of Tashkumyr, Osh Province. The
location was first discovered by Verzilian NN in 1965. In 2000 a joint
German-Russian-Kyrgyzstanian team went on a mammal hunt. As is often the case, this wasn't
as simple as it may sound.
A little light digging
About two tons of sediment were collected and screenwashed in the stream using the Henkel
process. This produced fifteen kilos of fragments of about the right sort of size; 0,5 -
2mm. That material was chemically treated in a laboratory which allowed more than 90% of
uninteresting debris to be discarded. The remaining particles were painstakingly studied
under a microscope. Two bits of tooth were independently recovered, and it was noticed that
they fitted together. A bit of glue allowed the fossil to be restored to its former, 1,7mm
long glory. The result is a slightly chipped but well-preserved lower
molar. The roots are missing.
Some of the neighbours
Other vertebrate fossils recovered at various times from the site include bits of shark,
fish, amphibian, turtle, lizard, pterosaur, dino and croc. A further molar was previously
tentatively identified as docodont, but it's too poorly preserved to be sure.
Architecture of a molar
The tooth of Tashkumyrodon is dominated by the centrally positioned cusp a. There are
a couple of crests running lengthways, (a-b and a-d), and two smaller ones going to the
sides, (a-g and a-c). Various other cusps and crests are also present, as is a fairly deep
basin at the front. That's a "pseudotalonid".
Basal characteristics include: the well-developed crests c-d,
c-f and b-e; the presence of a small part of the b-g crest; the unenlarged state of the
"pseudotalonid"; and the small size of cusp g. Amongst the
derived states are: the presence of an e-g crest; and the reduced state of crest b-g.
Only the bases of the roots are present. They were probably much the same size and separated
by a fairly wide, u-shaped notch. This is similar to most docodonts.
Holotype
The holotype is a lower left molar named ZIN 85279. I think it lives at the Zoological
Institute of the Russian Academy of Sciences in St Petersburg, but the paper doesn't seem
to include a list of abbreviations. The specific name is Latin for 'desired'.
With thanks to Marcel Opitz for posting the info. |
| Reference: | Martin & Averianov (2004), A new docodont (Mammalia) from
the Middle Jurassic of Kyrgyzstan, Central Asia. Journal of Vertebrate Paleontology, 24
(1), p.195-201. |
| Genus: Watch this space
Family: Tegotheriidae Tatarinov, 1994 |
| Species: | Not yet published-therium |
| Place: | Junggar Basin |
| Country: | China |
| Age: | Callovian, Middle Jurassic |
| Remarks: | A number of upper and lower
molars represent a new genus and species, which is close to
Tashkumyrodon. (With thanks to Dr Michael Maisch.) |
| Reference: | |
| Genus: Tegotherium
Tatarinov LP, 1994
Family: Tegotheriidae Tatarinov, 1994 |
| Species: | Tegotherium gubini Tatarinov LP, 1994 |
| Place: | Shar-Teeg Beds |
| Country: | Mongolia |
| Age: | Upper Jurassic (?) |
| Remarks: |
Thus far, this genus is known from one lower molar. It's
smaller than the equivalent teeth of the newly published and better preserved
Sibirotherium, which are between 1,6 and 1,9 times longer, (Maschenko et al 2002
(p.80).
An Asian radiation?
Tegotheriids are thought to be endemic to Asia. Their lower molariform teeth display a
mixture of basal and derived
docodont characteristics. Amongst the former are: a well developed cuspule e and a well
developed crest between the cusps b and e. The derived states include: an enlarged basin
at the front (a 'pseudotalonid'); an enlarged cusp g;
no crest between the cusps b and g, but one between e and g; no crest c-d, but one between
f and c; and an additional cingular cuspule known to its admirers as ee.
However, three of these characteristics are known from Simpsonodon: the enlarged
'pseudotalonid' and cusp g, and no crest c-d. This seems to be a matter of convergence,
(Machenko et all 2002, p.76)...
... though perhaps not, (Sigogneau-Russell 2003, p.361). She reports that Tegotherium:
"shares with Krusatodon a number of characters: the vertical furrows of the
main cusp, which are weak are absent in other taxa,
proportions of labial and
lingual cusps, crest between the mesio-labial cusp and the protruding mesio-lingual
cuspule. A generic identity is thus possible, but only direct comparison of the specimens
could ascertain it." Krusatodon is also, like Simpsonodon, from the
Middle Jurassic of Oxfordshire. These similarities suggest at least the possibility that
tegotheriids might not be restricted to Asia.
As regards a taxon I'm not presently employing, Asiadocodonta Martin & Averianov, 2001:
"this concept should be reviewed with respect to the new material from Kirtlington and
also take into account the individual variability of these teeth." [Update: Martin
& Averianov, 2004 maintains supports for a distinct Asiatic
taxon without representatives from Oxfordshire.]
She seems to state this genus was established in 1974. This is contrary to information in
Machenko et al, 2002, and McKenna & Bell, 1997, both of whom cite the later year. I just
checked.
And now for another source
Kielan-Jaworowska et al, 2000 briefly addresses Tegotherium. Had they been
in a position to notice it, then sauropod dinosaurs
would've been well advised to thank their lucky stars that this ferocious mammal
weren't about 100 times bigger. Precisely how large it was is subject to some
degree of uncertainty, given the limited information provided by a single tooth.
Nevertheless, as it's only 1.25 millimetres long, the owner can't have been exactly
ginormous.
The 2000 review doesn't use the current terminology for the three main cusps on the
crown but, as I read it in consultation with the 2005 description of
Itatodon, the appropriate designations appear clear
enough to me. Originally, the tooth was described as being from a
"symmetrodont", but it would've been a very
deviant one. There are three main cusps. The largest, a, is on the
buccal side and two lower cusps, b and c, occupy the
lingual margin. However, the main cusp occurs
towards the rear of the crown rather than nearer the mid-line, and that's not a
"symmetrodont" approach to things. There's also a basin in front of that main cusp
(positioned externally of lingual cusp b), and this is the
"pseudotalonid" of some docodont lower molars.
The crown also features a cingulum at the
rear.
Comparisons with other Asiatic docodonts weren't possible at the time, and for the
understandable reason that none were known.
Holotype
PIN 4174/67 is a right lower molar in the collection of the Paleontological Institute
of Moscow.
(Thanks are due to Vince Ward for some details.) |
| Reference: | Tatarinov (1994), On an unusual mammalian tooth from the
Mongolian Jurassic. Paleontologiceskii Zhurnal, 2, p.97-105 [in Russian]. |
| Help:
Should anybody have any further information, I'd be pleased to hear of it.
Regarding references and Bibliography:
I haven't and can't verify all the references, so beware. Traditional papers used in
constructing this page are in the bibliography. If you feel these are too few, then send
some more.
With thanks to all the featured sources.
back to top
Trevor Dykes, May 2001 Latest update: 21.12.2007
Ktdykes@arcor.de |
| With further thanks for assistance due to:
Dr Thomas Martin, Freie Universitaet, Berlin, for his comments on Guimarota, Portugal.
Mr Paul Ensom, Natural History Museum, London, for his advice on the Dorset Peraiocynodon.
Dr Richard Cifelli, Oklahoma Museum of Natural History, for his insights on Jugulator, tolerance of my sense of humour and etc.
Professor Pascal Godefroit, for the interesting and informative papers on microvertebrates from Western Europe.
Mr David Marjanovic, for corrections and suggestions.
Dr Zhexi Lou for the encouragement, kind words and various papers.
HitBox Central for the thrilling animations.
Dr John Alroy, for information concerning Jugulator, via his
North American Fossil Mammal Systematics Database
The Society of Vertebrate Paleontology's Bibliography of Fossil Vertebrates (John Damuth)
http://www.bfvol.org/
BIOSIS: The Index to Organism Names
http://www.biosis.org.uk/triton/indexfm.htm
Polyglot Paleonotologist
http://www.uhmc.sunysb.edu/anatomicalsci/paleo/terms.html
This homepage is packed with goodies, especially for the keen anatomist. |
Bibliography:
Averianov AO, (2002), Early Cretaceous "symmetrodont" mammal
Gobitheriodon from Mongolia and the classification of "Symmetrodonta".
Acta Palaeontologica Polonica 47 (4), p.705-716.
Averianov AO, (2004), Interpretation of the Early Cretaceous mammal
Peraiocynodon (Docodonta) and taxonomy of some British Mesozoic docodonts,
Russian Journal of Theriology, 3(1), p.1-4.
Averianov AO, Lopatin AV, Skutschas PP, Martynovich NV, Leshchinskiy SV, Rezvyi AS,
Krasnolutskii SA & Fayngertz AV, (2005), Discovery of Middle Jurassic mammals from
Siberia, Acta Palaeontologica Polonica, 50(4), p.789-797.
Averianov AO & Skutschas P (2000), A eutherian mammal from the Early Cretaceous
of Russia and biostratigraphy of the Asian Early Cretaceous vertebrate assemblages.
Lethaia 33(4), p.330-340.
Cox B, Dixon D, Gardiner B & Savage RJG (1989): Dinosaurier und andere Tiere der
Vorzeit, Mosaik Verlag (Sonderausgabe für Gondrom Verlag, 1994), ISBN 3 8112 1138 2
Engelmann GF & Callison G (1998), Mammalian Faunas of the Morrison Formation,
Modern Geology, Vo 34 (4), p.343-379.
Ensom P (1998): Discover Dorset: Geology, Dovcote Press, ISBN 1 874336 520
Freeman EF (1979), A Middle Jurassic Mammal Bed from Oxfordshire, Palaeontology,
22(1), p.135-166.
Godefroit P (1997), Reptilian, therapsid and mammalian teeth from the Upper Triassic
of Varangéville (northeastern France). Sciences de la Terre 67, p.83-102.
Godefroit P & Cuny G (1997): Archosauriform Teeth from the Upper Saint-Nicolas-
de-Port (Northeastern France). Palaeovertebrata, Montpellier 26 (1-4), p.1-34.
Ji Q, Luo Z-X, Yuan C-X & Tabrum AR (2006), A swimming mammaliaform from the
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Kemp TS (2005), The Origin and Evolution of Mammals, Oxford University Press,
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from the Meozoic of Mongolia, p.573-626 in Benton MJ, Shishkin MA, Unwin AM
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for evolution of the mammalian ear. Bulletin Museum of Comparative Zoology, Vol.156 (1),
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Mesozoic mammals. APP 47 (1), p.1-78.
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Northeastern Wyoming, Modern Geology 23, p.381-392.
Martin T (2005), Postcranial anatomy of Haldanodon exspectatus (Mammalia,
Docodonta) from the Late Jurassic (Kimmeridgian) of Portugal and its bearing for mammalian
evolution, Zoological Journal of the Linnean Society, 145, p.219-248.
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Jurassic of Kyrgyzstan, Central Asia. Journal of Vertebrate Paleontology, 24(1),
p.195-201.
Martin T & Nowotny M (2000), The docodont Haldanodon from the Guimarota
mine, p.91-96 in Martin T & Krebs B (eds), Guimarota - A Jurassic Ecosystem, Verlag Dr
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docodont from the Patagonian Late Cretaceous: evolutionary implications for Gondwanan
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mammal from the Late Jurassic of the Junggar Basin in northwest China, Acta Palaeontologica
Polonica, 50(4), p.799-808.
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